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Rebuild the POST tables from Ardent Tool's reproduction of IBM's own symptom/FRU lists: the previous tables mixed PC/AT-era meanings into PS/2 codes and contained codes not in IBM's list; '161 replace Dallas DS12887' was wrong (the Model 50 takes a 6 V pack, FRU 72X8498 - no Dallas module is fitted); correct the beep codes to IBM's five patterns; delete the ECA section (ECA 092 is verifiably the 8570 Data Modification Patch, ECA 087 cannot be corroborated), the unsourced PSU wattage and the S...
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[[File:IBM PS-2 Model 50 (photo).jpg|thumb|right|300px|IBM PS/2 Model 50. Source: Wikimedia Commons.]]
[[File:IBM PS-2 Model 50 (photo).jpg|thumb|right|300px|IBM PS/2 Model 50. Source: Wikimedia Commons.]]
This guide covers diagnostic procedures and the complete IBM PS/2 numeric POST error code reference applicable to the '''[[IBM PS/2 Model 50]]''' (machine type 8550, both the original 8550-021 and the 8550-031 / 061 Model 50 Z).


== Audio Beep Codes ==
This guide covers diagnostics for the '''[[IBM PS/2 Model 50]]''' (machine type 8550 โ€” the original 8550-021 and the 8550-031 / -061 Model 50 Z), and carries this wiki's reference copy of '''IBM's PS/2 numeric POST error code list''', which the Model 60, 70 and 80 guides link to rather than repeat.


{| class="wikitable styled-table" style="width:100%; text-align:center;"
'''What changed here, and why it matters.''' An earlier version of this page carried a hand-transcribed error-code table in which a number of entries were PC/AT-era meanings applied to PS/2 codes, several codes did not exist in IBM's list at all, and the 161 entry told the reader to replace a '''Dallas DS12887 RTC module''' โ€” a part the Model 50 does not have. The tables below are transcribed from the Ardent Tool of Capitalism's error-code pages, which reproduce IBM's own symptom-and-FRU lists, and they keep IBM's '''FRU / action''' column, which is the part you can act on.<ref name="ard_err" />
|+'''Model 50 power-on audio codes'''
== POST beep codes ==
ย 
These are IBM's PS/2 audio codes as published by the Ardent Tool of Capitalism. '''There are five of them, and three of the five mean the same thing.'''<ref name="ard_err" />
ย 
{| class="wikitable styled-table" style="width:85%; text-align:left;"
|+'''PS/2 beep codes''' (* = short beep, _ = long beep)
! Pattern !! Meaning
! Pattern !! Meaning
|-
|-
| 1 short || POST OK
| <code>*</code> || Normal operation
|-
| <code>* *</code> || A problem exists โ€” check the configuration. Run diagnostics if no error code is displayed
|-
|-
| 2 short || Numeric error displayed on screen
| <code>_ *</code> || Display or display adapter problem
|-
|-
| 1 long + 1 short || Display or display adapter problem
| <code>_ * *</code> || Display or display adapter problem
|-
|-
| 1 long + 2 short || Display or display adapter problem (alt path)
| <code>_ * * *</code> || Display or display adapter problem
|-
|-
| 1 long + 3 short || EGA / advanced display problem
| <code>* * * * * *</code> (continuous short beeps) || Check the keyboard
|-
|-
| Continuous short beeps || Keyboard problem &mdash; check fuse, cable, 8042
| Continuous solid beep || System board
|}
ย 
'''Earlier versions of this page gave a longer beep table''' that assigned distinct meanings to the three long-plus-short patterns โ€” including an "EGA / advanced display" fault on machines with integrated VGA โ€” and added two rows ("click then no beep", "no display and no sound") that are not beep codes at all. Those have been removed. The two symptoms are real and are dealt with under [[#Dead system|Dead system]] below, which is where IBM's own procedure puts them.
ย 
== Numeric POST error codes ==
ย 
'''How to read the code.''' IBM's error messages are eight characters, in a '''4 + 4''' form: the first four digits are the '''major''' error code and the last two significant digits the '''minor''' (diagnostic) code, with trailing zeros to fill. The major code is largely the same as the PC/AT error codes. A message that appears as three, four or five characters is the same code abbreviated: '''add two zeros to the right and pad with zeros on the left to reach eight characters.'''<ref name="ard_err" />
ย 
{| class="wikitable styled-table" style="width:75%; text-align:left;"
|+'''IBM's own examples'''
! Abbreviated !! Eight-character form
|-
|-
| Continuous solid beep || System board failure
| <code>301</code> (codes 300โ€“999) || <code>0003 0100</code>
|-
|-
| Click then no beep || PSU started but Power Good not asserted in 150 ms &mdash; shorted planar tantalum
| <code>1701</code> (codes 1500โ€“2999) || <code>0017 0100</code>
|-
|-
| No display, no sound || PSU fold-back from a planar short
| <code>16680</code> (codes 15000โ€“19999) || <code>0166 8000</code>
|}
|}


== Numeric POST Error Codes ==
If a message appears as twelve characters, disregard the last four. The minor code depends on the error type and is mostly only specified when running Advanced Diagnostics, though it often appears at POST too; where the lists below show '''XX''' it means "don't care".<ref name="ard_err" />


The Model 50 uses the standard PS/2 Major/Minor numeric error format. MCA-specific codes (especially 165 card-ID-mismatch) are critical for this generation.
=== Codes 100โ€“159 โ€” system board ===


=== 1xx โ€” System Board ===
{| class="wikitable styled-table" style="width:100%; text-align:left;"
ย 
|+'''Error codes 100โ€“159, with IBM's FRU and action list'''
{| class="wikitable styled-table" style="width:100%; text-align:center;"
! Code !! Symptom !! FRU / action
|+'''Major code 1xx โ€” system board'''
|-
! Code !! Meaning
| 0001 01XX || Interrupt failure. Possibly a bad battery or processor || Run Advanced Diagnostics
|-
|-
| 101 || Interrupt failure (8259A PIC)
| 0001 02XX || ROM checksum or timer error. Possibly a bad battery or processor || Run Advanced Diagnostics
|-
|-
| 102 || Timer 0 failure / BIOS ROM checksum error
| 0001 0300 || Checksum or timer error || Processor board, then system board
|-
|-
| 103 || Timer interrupt failure or 2 KB CMOS RAM test
| 0001 02XX / 03XX / 04XX / 07XX || โ€” || System board, then processor board
|-
|-
| 104 || 80286 protected mode failure
| 0001 05XX || Command not accepted || '''Information only'''
|-
|-
| 105 || Last 8042 keyboard controller command not accepted
| 0001 06XX || Converting logic test failure || Run Advanced Diagnostics
|-
|-
| 106 || Converting logic test
| 0001 07XX / 08XX / 09XX || Interrupt or memory failure || System board memory, system board, any adapter, bus adapter
|-
|-
| 107 || NMI test (parity check)
| 0001 10XX || Check memory || Memory module kit, then system board
|-
|-
| 108 || Timer bus test (8253/8254)
| 0001 11XX || I/O channel check || Adapter memory, expansion adapter, system board
|-
|-
| 109 || DMA (8237) test error
| 0001 12XX / 13XX || Possible Micro Channel timeout error. Often caused by a card with a defective MCA bus interface, or a card too slow to respond || System board, processor board, any adapter
|-
|-
| 110 || Planar parity error
| 0001 14XX || ROM error || Any adapter, bus adapter
|-
|-
| 111 || I/O parity error (MCA adapter)
| 0001 15XX || '''80386 protected mode failure'''; BIOS checksum error || System board
|-
|-
| 112 || Watchdog timeout (MCA adapter failure)
| 0001 16XX || Possible read/write problem || Run Advanced Diagnostics
|-
|-
| 113 || DMA arbitration timeout (MCA adapter failure)
| 0001 18XX || Previously detected error || System board memory, processor board
|-
|-
| 114 || External ROM checksum error
| 0001 19XX || 2.88 MB diskette drive installed but not supported || Run Automatic Configuration, then system board
|-
|-
| 121 || Unexpected hardware interrupt
| 0001 20XX || Possible processor self-test failure || Processor cache, processor board
|-
|-
| 151 || Bad battery
| 0001 21XX || Problem detected during memory remapping (256 KB ROM error) || '''Information only'''
|-
|-
| 152 || RTC or CMOS error
| 0001 22XX || POST found a hardware error || Run Advanced Diagnostics
|-
|-
| 160 || Planar ID not recognised &mdash; loose MCA riser
| 0001 30XX || POST could not start the operating system. Is the boot drive in the selectable drive sequence? || Check the drive sequence
|-
|-
| 161 || CMOS empty &mdash; '''replace Dallas DS12887 RTC'''
| 0001 3002 || Drive startup sequence is corrupt or invalid || Run Automatic Configuration and reset the sequence; if it persists, replace the system board
|-
|-
| 162 || CMOS checksum mismatch
| 0001 3003 || EEPROM could not be read || Run Automatic Configuration; if it persists, replace the system board
|-
|-
| 163 || Time and date not set
| 0001 32XX || DMA extended registers error || Run Advanced Diagnostics
|-
|-
| 164 || Memory size error &mdash; run SETUP
| 0001 33XX || DMA verify function error โ€” logic failed || Run Advanced Diagnostics
|-
|-
| 165 || '''Card ID mismatch''' &mdash; run Auto Configuration from Reference Diskette
| 0001 34XX || DMA arbitration logic error || Run Advanced Diagnostics
|-
|-
| 166 || MCA card busy error
| 0001 4908 / 4909 || โ€” || Check the cover lock and tamper-evident switches '''before''' replacing any FRU
|-
|-
| 167 || RTC not updating
| 0001 52XX || Real time clock error. '''Not always a hardware failure''' || Run Advanced Diagnostics
|-
|-
| 199 || User-indicated configuration not correct
| 0001 56XX || Security error โ€” covers removed without the key; tamper-evident switch tripped || Reconfigure from the Reference Diskette; then the security switch assembly, then the system board
|}
|}


==== 165 card ID mismatch ====
'''Note what is not in IBM's list:''' there is no 104 "protected mode failure" (that is 115), no 121 "unexpected hardware interrupt" (121 is a memory-remapping note and is information only), and no 151 at all.<ref name="ard_err" />


The single most common POST error on a Model 50 with any installed MCA cards. Occurs when:
=== Codes 160โ€“199 โ€” configuration, battery and security ===


* A new MCA card has been added since the last Auto Configuration run.
{| class="wikitable styled-table" style="width:100%; text-align:left;"
* An existing card has been removed.
|+'''Error codes 160โ€“199, with IBM's FRU and action list'''
* An ADF (Adapter Definition File) is missing from the working Reference Diskette.
! Code !! Symptom !! FRU / action
* An MCA card's edge fingers are dirty and the card is intermittently reporting a different ID.
|-
| 0001 60XX || System board ID not recognised. Possible system board failure || Run Advanced Diagnostics
|-
| 0001 61XX || '''Battery.''' IBM's own caution: the lithium battery presents a fire, explosion or severe burn risk, and using another battery could cause ignition or explosion || '''Battery''', then complex, system board, bus adapter
|-
| 0001 62XX || Be sure all devices are powered on. Check enable/disable settings. Configuration changed? Run Automatic Configuration || Any device, then battery
|-
| 0001 63XX || Date and time error || Set the date and time
|-
| 0001 6000 / 6400 / 6500 / 6700 / 6900 || If setting configuration, date and time does not solve it, check the devices list || Set configuration and features, then system board
|-
| 0001 66XX || Adapter busy. Reseat all adapters || Run Advanced Diagnostics
|-
| 0001 67XX || Clock is not working correctly || Set features; set date and time
|-
| 0001 68XX || Real time clock error. '''This is not always a hardware failure''' || Run Advanced Diagnostics
|-
| 0001 69XX || Processor configuration error || Run Automatic Configuration and verify the processor configuration '''before''' replacing FRUs
|-
| 0001 70XX || ASCII console setup conflict โ€” the serial port is disabled || From Set Configuration, Change Configuration, enable the port
|-
| 0001 73XX || '''Possibly a weak battery'''; bad CMOS/NVRAM checksum || Set configuration / features
|-
| 0001 74XX || If the configuration has changed run Automatic Configuration, otherwise Advanced Diagnostics || Any device, system board, bus adapter
|-
| 0001 75XX || Security error โ€” the system board EEPROM failed || System board
|-
| 0001 76XX || Security error โ€” covers removed without the key || Reconfigure, then security switch assembly, then system board
|-
| 0001 77XX / 78XX || Security error โ€” passwords corrupted. Reset passwords || System board
|-
| 0001 79XX || System error log might be full || Read and note the errors, clear the log, then run Advanced Diagnostics
|-
| 0001 81XX || The machine needs a network adapter for remote IPL, or a hard disk with ID LUN 0 for IML; neither was detected || Run Automatic Configuration, then network adapter, hard disk, system board
|-
| 0001 82XX || Privileged access password data is corrupted || '''Information only''' โ€” move jumper JMP2 to position 0, write enabled, to restore it
|-
| 0001 83XX || Wrong password entered || Enter the privileged access password, not the power-on password
|-
| 0001 84XX || Power-on password corrupted || The user must reset the password
|-
| 0001 85XX || Selectable startup sequence corrupted || Run the Select Startup Sequence utility
|-
| 0001 86XX || Security error, hardware failed || Run Advanced Diagnostics, then system board
|-
| 0001 87XX || Vital Product Data error โ€” system serial number corrupted || Set system identification and retype the serial number; if it persists, suspect the system board
|-
| 0001 88XX || Vital Product Data error || Run Automatic Configuration
|-
| 0001 89XX || The wrong password was entered three times || '''Information only''' โ€” clear the system error log and restart
|-
| 0001 91XX || 82385 cache test failed || Run Advanced Diagnostics
|-
| 0001 99XX || User indicated the configuration is invalid || System board
|-
| 0001 XXXX (not listed) || โ€” || Planar / complex, any adapter, bus adapter
|}


Resolution: boot the Reference Diskette, select '''Backup the Reference Diskette to a working diskette''' if you do not have a working copy, then '''Set Configuration โ†’ Run Auto Configuration'''. Insert each option diskette as prompted to load missing ADFs.
'''The 161 entry is a battery entry, not an RTC-module entry.''' See [[#Battery|Battery]] below for which battery this machine actually takes.


==== 161 / 162 / 163 cluster ====
'''162 is not a checksum error.''' IBM's 162 tells you to check that devices are powered on and that the configuration has not changed; the bad-checksum code is '''0001 73XX''', and IBM's note there is "possibly a weak battery".<ref name="ard_err" />


Dead Dallas DS12887 RTC battery. Replace per [[IBM PS/2 Model 50 Maintenance Guide]] and re-run SETUP from the Reference Diskette.
=== Codes 200โ€“299 โ€” memory ===


=== 2xx โ€” Memory ===
{| class="wikitable styled-table" style="width:100%; text-align:left;"
ย 
|+'''Error codes 200โ€“299, with IBM's FRU and action list'''
{| class="wikitable styled-table" style="width:100%; text-align:center;"
! Code !! Symptom !! FRU / action
|+'''Major code 2xx โ€” memory'''
|-
! Code !! Meaning
| 0002 01XX / 05XX || Reseat system board memory || System board memory, then system board
|-
| 0002 0XXY / 17XY || Memory failure || System board memory, memory riser card, processor board; then system board
|-
| 0002 10XX / 11XX || Check memory || Processor board, system board memory, memory riser card, system board
|-
| 0002 11CZ || Missing or unsupported memory module โ€” none installed, or one that does not provide the required presence-detect coding || Memory module, system board
|-
| 0002 15UZ || No system memory is installed || Memory module, system board
|-
| 0002 14XX / 15XX / 16XX / 21XX / 26XX / 35XX / 40XX / 41XX || '''Check memory. It might be the wrong type or the wrong speed''' || System board memory, memory riser card; then system board, processor board; then bus adapter
|-
|-
| 201 || Memory test failed. The hex digits preceding "201" identify the failing 64 KB bank and bit
| 0002 21XX || ROM to RAM parity error || System board
|-
|-
| 202 / 203 || Memory address line failure (0โ€“15 / 16โ€“23)
| 0002 35XX || Single-bit (correctable) ECC memory error || Processor / system board, then system board memory
|-
|-
| 207 || ROM failure
| 0002 51XX || Memory location changed on the memory expansion option || '''Information only'''
|-
|-
| 211 || Base 64 K on I/O channel failed (planar SIMMs)
| 0002 55XX || Check memory || System board memory, then system board
|-
|-
| 215 / 216 || Base 64 K on daughter card failed (MCA memory adapter)
| 0002 9000 || Unsupported memory combination detected || Correct the combination of ECC and parity modules, run Automatic Configuration, rerun Advanced Diagnostics
|-
|-
| 221 || ROM-to-RAM mapping error (latches until fixed)
| 0002 91XXโ€“94XX, 9800 || Checksum value mismatch || Run Automatic Configuration, then rerun Advanced Diagnostics
|-
|-
| 225 || Wrong / defective / slow memory &mdash; check 125-ns vs 85-ns SIMM
| 0002 95XX / 96XX || Check memory for an unsupported configuration or modules || System board memory
|}
|}


A 225 error on a Model 50 that previously worked usually means the wrong-speed SIMM was fitted (85-ns where 125-ns belongs, or vice versa, or a non-PS/2-pinout SIMM).
'''The "last two digits identify the failing module" rule applies only to the Models 56/57, 76/77, 85 and 90/95.'''<ref name="ard_err" /> On the earlier machines the 2xx minor code does not decode to a socket, and the PC/AT-era reading in which the digits before "201" identify a failing 64 KB bank and bit is not the PS/2 behaviour. Earlier versions of this page said otherwise.


=== 3xx โ€” Keyboard ===
=== Codes 300โ€“999 โ€” keyboard, ports, display, diskette, coprocessor ===


{| class="wikitable styled-table" style="width:100%; text-align:center;"
{| class="wikitable styled-table" style="width:100%; text-align:left;"
|+'''Major code 3xx โ€” keyboard'''
|+'''Error codes 300โ€“999, with IBM's FRU and action list'''
! Code !! Meaning
! Code !! Symptom !! FRU / action
|-
| 0003 01XX / 02XX || โ€” || Keyboard cable, then system board
|-
| 0003 03XX / 04XX || โ€” || System board, keyboard, keyboard cable
|-
| 0003 05XX || Keyboard voltage error || Keyboard port fuse, keyboard cable, system board. '''If there is no fuse in the system, replace the system board'''
|-
| 0003 06XX || Unsupported keyboard attached || Check for an unsupported keyboard
|-
| 0003 07XX || โ€” || Keyboard, keyboard cable
|-
| 0003 20XX || โ€” || System board
|-
| 0004 01XX || โ€” || System board. '''On the 90/95 this is a parallel port error, not a video error'''
|-
| 0004 02XXโ€“05XX || โ€” || System board
|-
| 0005 XXXX || โ€” || Display adapter, any type
|-
| 0006 01XX || โ€” || Defective diskette, diskette drive, system board
|-
|-
| 301 || Keyboard did not respond / stuck key. The XX value preceding "301" is the scan code. Also occurs if keyboard plugged into mouse port
| 0006 02XX || Invalid boot record || Defective diskette
|-
|-
| 302 || User-indicated keyboard test failure
| 0006 04XX || Unsupported drive or cable โ€” the drive must be a media-sense type || Diskette drive, system board, diskette drive cable
|-
|-
| 303 || Keyboard or 8042 controller error
| 0006 05XX || Diskette drive error || Run Advanced Diagnostics
|-
|-
| 304 || Planar (8042) error / CMOS does not match keyboard
| 0006 06XXโ€“60XX (most) || '''Generally media errors.''' Try a known-good diskette; if the error returns, replace the drive || Diskette, diskette drive, system board
|-
|-
| 305 || +5 V keyboard fuse blown โ€” replace fuse on planar
| 0006 62XX || Wrong drive type installed || '''Information only'''
|-
| 0006 63XX || Wrong media type in the drive || '''Information only'''
|-
| 0007 XXXX || '''Math coprocessor.''' For a 486 processor, erase COPROC.DGS from the backup Reference Diskette, restore the system partition from the corrected backup, and rerun Advanced Diagnostics || Math coprocessor, then system board
|}
|}


=== 4xx / 5xx โ€” Integrated VGA ===
'''The math coprocessor family is 7xx, not 8xx.'''<ref name="ard_err" /> Earlier versions of several pages in this family headed it "8xx โ€” Math Coprocessor" with a single "801" code. In IBM's list 0008 does not exist and 0018 XXXX is the system board expansion unit.


* 401 โ€” Planar VGA error (monochrome path).
'''401 is not a video code on the machines where IBM annotates it''' โ€” it is a parallel port error on the 90/95 and otherwise a system board FRU. The general display-adapter family is '''0005 XXXX'''.<ref name="ard_err" />
* 501 โ€” Planar VGA error (colour path).
* 2401 โ€” Diagnostic VGA error.
* 2408 โ€” VGA ground circuit fault.


=== 6xx โ€” Diskette ===
=== Codes 1500โ€“2999 โ€” ST-506 fixed disk and video ===


Standard PS/2 6xx codes. The 6xx codes cover the planar floppy controller and the 1.44 MB drive.
{| class="wikitable styled-table" style="width:100%; text-align:left;"
|+'''Error codes 1500โ€“2999 (selected), with IBM's FRU and action list'''
! Code !! Symptom !! FRU / action
|-
| 0017 01XX / 03XX / 04XX / 14XX, and any 0017 XXXX not listed below || โ€” || ST-506 hard disk drive, cable, adapter; then system board; then '''power supply'''
|-
| 0017 02XX || โ€” || ST-506 hard disk adapter
|-
| 0017 05XXโ€“91XX (most) || '''Read/write problem.''' Confirm the drive type is supported; if it is, try a low-level format; if the error continues, replace the drive || Format the drive, then the drive
|-
| 0018 0100โ€“0700 || โ€” || System board
|-
| 0018 6XXX || โ€” || Set configuration / features, then battery
|-
| 0018 XXXX (not listed) || โ€” || System board expansion unit
|-
| 0024 0100 / 0200 || '''If the screen colours change''' || Display, any type
|-
| 0024 0100 / 0200 || '''If the screen colours are correct''' || System board, then display
|-
| 0024 0900 || โ€” || Display, any type
|-
| 0024 1000 || โ€” || System board
|}


* 601 โ€” Drive or controller test failed.
'''There is no 2403 or 2408 in IBM's list.''' The 24xx family is four entries, and IBM's own discriminator for two of them is whether the screen colours change.<ref name="ard_err" />
* 602 โ€” Boot record invalid.
* 606โ€“626 โ€” Verify / format / read / write / NEC / DMA / seek / CRC / address-mark errors.
* 650 โ€” Drive speed error.
* 651โ€“656 โ€” Format / verify / read / write / controller / drive failures.
* 657โ€“660 โ€” Write-protect or change-line signal stuck.


=== 7xx โ€” 80287 Math Coprocessor ===
=== Codes 10400โ€“10499 โ€” ESDI fixed disk ===


7xx errors raised only if software invokes the 80287. POST does not run a 80287 test unless explicitly enabled.
This is the family most often reproduced wrongly. '''IBM's list is not a consecutive run of codes''', and several codes that circulate widely are not in it at all.


=== 17xx โ€” ST-506 Fixed Disk ===
{| class="wikitable styled-table" style="width:100%; text-align:left;"
ย 
|+'''ESDI error codes, with IBM's FRU and action list'''
For Model 50 (8550-021) and Model 50 Z 30 MB (8550-031) with the ST-506 Fixed Disk Adapter/A:
! Code !! Symptom !! FRU / action
ย 
|-
{| class="wikitable styled-table" style="width:100%; text-align:center;"
| 0104 50XX / 51XX / 90XX / 91XX / 92XX / 99XX || ESDI read/write error || Run Advanced Diagnostics, riser card if installed, ESDI drive, system board
|+'''Major code 17xx โ€” ST-506 fixed disk'''
|-
! Code !! Meaning
| 0104 52XX || ESDI seek test error || Run Advanced Diagnostics
|-
| 0104 53XX || ESDI โ€” wrong drive type? || '''Information only'''
|-
|-
| 1701 || Controller POST error
| 0104 54XX || ESDI sector buffer test error || Run Advanced Diagnostics
|-
|-
| 1702 || Controller timeout
| 0104 55XX / 56XX || ESDI controller error || Run Advanced Diagnostics
|-
|-
| 1703 || Drive seek failure
| 0104 59XX || ESDI drive diagnostic command error || '''Information only'''
|-
|-
| 1780 || Drive 0 timeout at IPL (drive not up to speed / stiction / cable off)
| 0104 61XX || ESDI drive format error || Run Advanced Diagnostics
|-
|-
| 1790 / 1791 || Format not recognised / data cable off
| 0104 62XX || ESDI '''controller seek''' error || Run Advanced Diagnostics
|}
ย 
=== 104xx โ€” ESDI Fixed Disk ===
ย 
For Model 50 Z 60 MB (8550-061) with the ESDI Fixed Disk Adapter/A:
ย 
{| class="wikitable styled-table" style="width:100%; text-align:center;"
|+'''Major code 104xx โ€” ESDI'''
! Code !! Meaning
|-
|-
| 10450 || Replace drive (read-write test failed)
| 0104 64XX || ESDI hard disk '''read''' error || Run Advanced Diagnostics
|-
|-
| 10451 || Replace drive (read-verify test failed)
| 0104 67XX || ESDI drive '''non-fatal''' seek error || Run Advanced Diagnostics
|-
|-
| 10452 || Replace drive (seek test failed)
| 0104 68XX || ESDI drive '''fatal''' seek error || Run Advanced Diagnostics
|-
|-
| 10454 || Controller (sector buffer test failed)
| 0104 69XX || ESDI drive soft error count exceeded || Run Advanced Diagnostics
|-
|-
| 10455 || Controller failure
| 0104 70XX / 71XX / 72XX || ESDI '''controller wrap''' error || Run Advanced Diagnostics
|-
|-
| 10463 || Drive (read/write sector error)
| 0104 73XX || ESDI corrupt data. A low-level format might be required || '''Information only'''
|-
|-
| 10465 / 10466 || Controller (ECC error)
| 0104 80XX || โ€” || ESDI drive, drive cable, ESDI controller, system board, riser card (Models 50, 55, 70 where applicable)
|-
|-
| 10480 / 10481 || Drive 0 / 1 seek failure
| 0104 81XX || ESDI drive D seek error || Run Advanced Diagnostics
|-
|-
| 10490 / 10491 || Drive 0 / 1 read failure
| 0104 82XX || ESDI '''drive select acknowledgement bad''' || Run Advanced Diagnostics
|}
|}


=== 8602 โ€” Pointing device ===
'''Codes that are not in IBM's list and have been removed from this wiki:''' 10463, 10465, 10466, 10484, 10485, 10486, 10487, 10488, 10489 and 10493. '''Codes whose meaning was wrong:''' 10462 (controller seek, not a controller-side read failure), 10464 (hard disk read error, not a boot-record failure), 10470/10471/10472 (all three are controller wrap errors, not drive timeout, drive busy and status error), 10473 (corrupt data, not a read-verify error) and 10482 (drive select acknowledgement, not controller failure). '''Code 10459 was missing.'''
ย 
=== Other families ===


* 8601 / 8603 / 8604 โ€” mouse / 8042 errors. Most commonly a mouse plugged into the keyboard port.
IBM's full listing runs to 29999 and includes adapter-specific families โ€” 0037 XXXX SCSI on the system board, 0074 XXXX 8514/A, 0075 XXXX XGA and display adapters, 0086 XXXX pointing device, 0096 XXXX SCSI adapter with cache, and more. It also has separate '''IML''' (I999xxxx / 0999xxxx) and '''SCSI''' (RDDDPLSCB QEET) code schemes. Consult the Ardent Tool of Capitalism's error-code pages for these rather than a per-machine summary.<ref name="ard_err" />


== Reference Diskette and Advanced Diagnostics ==
== Diagnostics procedure ==
ย 
IBM's own procedural notes, which change the order of work:<ref name="ard_err" />
ย 
* '''Cold-boot the Reference Diskette''' โ€” power on with the diskette already in the drive. Soft-booting it can produce false errors '''and''' a false indication that a power-on password is already set.
* '''If several errors appear, diagnose the first one first.''' The cause of the first can cause other devices to fail. This matters most with configuration errors.
* '''Always cold boot and run Advanced Diagnostics''' (System Programs, then Ctrl-A at the main menu) '''before replacing components.''' If the diagnostics do not fail, replacing parts probably will not help โ€” look at the software instead.
* If an adapter consists of several FRUs, '''remove the optional FRUs one at a time''' to see whether the symptoms change, before replacing the adapter.
* '''External surge suppressors''' are a documented source of hard-to-diagnose problems.


The Model 50 has '''no built-in SETUP'''. All configuration through the Model 50 Reference Diskette (version 1.07 final). Key procedures:
== Dead system ==


# Always '''cold-boot''' the Reference Diskette (insert before powering on). Warm-booting may report false errors.
'''No POST, blank screen, no beep.''' IBM's stated most likely cause is '''a device shorting out the power supply''' โ€” an improperly inserted memory module, a defective adapter or a defective device. '''The system board must present a Power Good signal to the power supply within 150 ms or the supply shuts itself down internally.''' That is the mechanism behind the "click and then nothing" symptom.<ref name="ard_err" />
# '''Backup the Reference Diskette''' to a working diskette on first use. The original is read-only.
# '''Set Configuration โ†’ View configuration''' shows the current state.
# '''Set Configuration โ†’ Run Auto Configuration''' runs MCA card detection and ADF lookup.
# '''Test the computer โ†’ Diagnostics''' runs the full hardware test suite.
# '''Press Ctrl-A''' from the main menu to enter '''Advanced Diagnostics''' (FRU-level testing with minor NN codes).


ADF files for MCA cards are supplied on the option diskette that ships with each card. Copy each ADF onto your working Reference Diskette before fitting the card.
IBM's list of the usual causes is blunt: a SIMM inserted backwards, an adapter not fully seated, the power cord not plugged in, an unsupported or defective adapter, or โ€” on a heavily loaded machine โ€” too many drives trying to spin up at once, which can be fixed by leaving the motor-start jumper open so the drives start after the controller interrogates them.<ref name="ard_err" />


== Dead System Isolation ==
The procedure:<ref name="ard_err" />


If the Model 50 shows no signs of life:
# '''Check the line cord at both ends.''' IBM singles this out: intermittent and very hard to diagnose faults, including unexpected power-on resets during operation, are caused by line cords that are not fully seated or are too loose to make a tight connection. Slightly forming the male contacts in the power supply connector may fix it, or the female contacts in the plug. '''Remove the cord from the outlet before working on its contacts.''' Replacing the cord is sometimes necessary.
# Remove all adapters, options and extra memory.
# Remove all external connections โ€” keyboard, mouse, display.
# Plug in, power on, and listen for a beep. A beep means POST has run; several beeps may occur.
# '''If no beep:''' verify continuity through the speaker. If the speaker is good, replace the system board memory and retry. If there is still no beep, measure the power supply voltages โ€” if they are correct, replace the system board; if they are wrong, replace the power supply.
# '''If a beep occurs:''' reinstall the adapters one at a time, retrying after each. When the beep stops, the last item fitted is the suspect. There is no need to reconfigure between steps, because all you are looking for is the beep.


# Verify mains power and the PSU fan turns.
'''On machines with LogicLock''', the switches that detect unauthorised access can be left in the wrong position when the case is reassembled, which produces a machine that appears dead or will not run with the cover removed.<ref name="ard_err" />
# Open the chassis.
# Verify PSU rails at the planar power connector with a multimeter.
# Pull all MCA cards. Try to boot with planar + riser + SIMM(s) + floppy only.
# Listen for a beep. If no beep, suspect bank-0 SIMM or planar power short.
# Re-add MCA cards one at a time. The failing card is the one that re-introduces the failure.


A shorted tantalum on the planar pulls the PSU into fold-back protection (Power Good not asserted within 150 ms) and produces a "click then nothing" symptom. Inspect the planar for shorted caps with a multimeter on diode test โ€” see [[IBM PS/2 Model 50 Capacitor Replacement Guide]].
== Battery ==


== ESDI Drive Stiction Recovery (8550-061) ==
'''Defective or weak batteries can cause the loss of all setup information. If only part of the setup is lost, the battery is probably NOT the cause.''' Inaccurate time is usually software, though some older models with 6 V batteries are prone to the clock running slow.<ref name="ard_batt" />


If a 60 MB ESDI drive does not spin up:
'''The Model 50 and Model 50 Z take a 6 V lithium battery pack, IBM FRU P/N 72X8498''' โ€” a two-cell pack, usually yellow with black ends, held in a dedicated Battery/Speaker Assembly. It is a camera battery: equivalents are the '''CR-P2''' (Varta, Panasonic, GP, Sony, Sanyo), '''DL223A''' (Duracell), '''EL223AP''' (Ever Ready), '''K223LA''' (Kodak) and '''PC223''' (Ray-O-Vac).<ref name="ard_batt" />


# Power off and remove the drive from its caddy.
'''There is no Dallas RTC module on a Model 50.''' The Dallas self-contained module (IBM FRU 8509237, Dallas DS1287) is fitted to the Models 25-286, 30-286, 35, 40, 55 SX and 55 LS and 65 SX โ€” not to the 50, 50 Z, 60, 70, 80, P70 or P75, which all use the 6 V pack.<ref name="ard_batt" />
# Hold horizontal and rotate gently around the spindle axis.
# Reinstall and power on.
# Frees a stuck spindle for one boot. Image the drive contents immediately and replace.


== Common Symptoms ==
If you are working on a machine that '''does''' take the Dallas module, two things are worth knowing: the DS1287 can be replaced by the pin-compatible '''DS12887''' (or DS12887+, the lead-free version), '''but do not use the DS12C887''' โ€” it uses the century byte differently and will not work in a PS/2.<ref name="ard_batt" />


* '''Click, no beep''' &mdash; shorted planar tantalum. Recap planar.
== 165 card ID mismatch ==
* '''161 / 162 / 163 at every boot''' &mdash; dead DS12887 RTC battery. Replace module.
* '''165 at every boot''' &mdash; run Auto Configuration from the Reference Diskette.
* '''201 with bank/bit prefix''' &mdash; identify failing SIMM by the prefix hex digits.
* '''225 after SIMM swap''' &mdash; wrong-speed SIMM (Model 50 needs 125-ns, Model 50 Z needs 85-ns) or non-PS/2-pinout SIMM.
* '''Drive not detected''' &mdash; ST-506 stiction, ESDI cable seated badly, or controller card edge contacts dirty.
* '''Random reboots under load''' &mdash; aged 94 W PSU electrolytics, often near rated load.
* '''VGA wrong colours''' &mdash; planar VGA gate array failing.
* '''Keyboard 305 / mouse 8603''' &mdash; ports swapped or keyboard fuse blown.


== ECA Recalls ==
The most common POST error on a Model 50 with any MCA cards fitted. It occurs when a card has been added or removed since the last Automatic Configuration run, when an ADF (Adapter Definition File) is missing from the working Reference Diskette, or when a card's edge fingers are dirty enough that it reports a different ID intermittently.


* '''ECA 087''' โ€” Model 50 Z planar replacement under certain serial number ranges (specific memory controller issue).
To clear it: boot the Reference Diskette, back it up to a working diskette if you have not already, then '''Set Configuration โ†’ Run Auto Configuration''', inserting each option diskette as prompted to load the missing ADFs. Copy the ADF for each MCA card onto your working Reference Diskette before fitting the card.
* '''ECA 092''' โ€” ESDI Fixed Disk Adapter/A firmware update for drive compatibility (Model 50 Z 60 MB units).


The IBM HMM (S52G-9971-02, October 1994) documents the affected serial number ranges for each ECA.
== Reference Diskette and Advanced Diagnostics ==


== โš ๏ธ Power-supply RIFA capacitor and tantalum shorts ==
The Model 50 has '''no built-in SETUP''' โ€” all configuration is done from the Model 50 Reference Diskette.


Two age-related failures are near-universal on this era of IBM hardware:
# '''Always cold-boot it''' (insert before powering on). Warm-booting can report false errors and falsely indicate that a power-on password is set.<ref name="ard_err" />
# '''Back the Reference Diskette up''' to a working diskette on first use. The original is read-only.
# '''Set Configuration โ†’ View configuration''' shows the current state.
# '''Set Configuration โ†’ Run Auto Configuration''' runs MCA card detection and ADF lookup.
# '''Test the computer โ†’ Diagnostics''' runs the hardware test suite.
# '''Ctrl-A''' from the main menu enters '''Advanced Diagnostics''', which produces the minor codes.


* '''RIFA mains-filter capacitors''' in the power supply are metallised-paper parts that crack and fail '''short''' with age, producing acrid smoke shortly after power-on. Replace them pre-emptively with modern X2-class parts.<ref name="ibm_rifa">[https://www.minuszerodegrees.net/failure.htm minuszerodegrees.net โ€” IBM failure symptoms]; [https://www.classic-computers.org.nz/blog/2010-11-04-restoring-an-IBM-xt.htm Repairing and Restoring an IBM XT]; and [https://retrorepairsandrefurbs.com/2025/05/15/1983-ibm-pc-5160-xt-power-supply-rebuild-modifications/ Adam's Vintage Computer Restorations]. Source for the RIFA mains-filter capacitor failing short (smoke) and the tantalum capacitors failing short and preventing the PSU from firing.</ref>
== ESDI drive stiction recovery (8550-061) ==
* '''Tantalum capacitors''' on the planar (system board) and on ISA cards fail short with age. A shorted tantalum will '''prevent the power supply from starting''' (dead machine, PSU protection latched) &mdash; look for a cracked or discoloured tantalum and lift suspect ones to find the short.<ref name="ibm_rifa">[https://www.minuszerodegrees.net/failure.htm minuszerodegrees.net โ€” IBM failure symptoms]; [https://www.classic-computers.org.nz/blog/2010-11-04-restoring-an-IBM-xt.htm Repairing and Restoring an IBM XT]; and [https://retrorepairsandrefurbs.com/2025/05/15/1983-ibm-pc-5160-xt-power-supply-rebuild-modifications/ Adam's Vintage Computer Restorations]. Source for the RIFA mains-filter capacitor failing short (smoke) and the tantalum capacitors failing short and preventing the PSU from firing.</ref>


IBM PC/XT switching supplies also need a '''minimum load''' to start, so a bare supply on the bench may not run without a dummy load.<ref name="ibm_rifa">[https://www.minuszerodegrees.net/failure.htm minuszerodegrees.net โ€” IBM failure symptoms]; [https://www.classic-computers.org.nz/blog/2010-11-04-restoring-an-IBM-xt.htm Repairing and Restoring an IBM XT]; and [https://retrorepairsandrefurbs.com/2025/05/15/1983-ibm-pc-5160-xt-power-supply-rebuild-modifications/ Adam's Vintage Computer Restorations]. Source for the RIFA mains-filter capacitor failing short (smoke) and the tantalum capacitors failing short and preventing the PSU from firing.</ref>
If the 60 MB ESDI drive does not spin up:


== โš ๏ธ CMOS / RTC battery ==
# Power off and remove the drive from its caddy.
# Hold it horizontal and rotate it gently around the spindle axis.
# Refit and power on.


This machine keeps its configuration in battery-backed CMOS, and the battery is a common failure. On AT-class boards the clock/CMOS is often a '''Dallas DS1287/DS12887''' module with the cell sealed inside; it lasts about ten years and then dies, giving '''161 / 163''' CMOS and clock errors at POST (and sometimes spurious floppy-drive errors). PS/2 planars use a rechargeable barrel or pack battery that '''leaks''' and corrodes the board. Replace a dead Dallas module (or rework it with an external coin cell), and on a leaking planar battery remove it and clean the corrosion before it eats the traces.<ref name="ibm_batt">[https://www.classic-computers.org.nz/blog/2009-10-10-renovating-a-dallas-battery-chip.htm Fixing a Flat Dallas DS1287 RTC], Classic Computers; and [https://www.ardent-tool.com/misc/Dallas_Rework.html Reworking Dallas RTC Modules], Ardent Tool. Source for the Dallas DS1287/DS12887 internal-battery death (161/163 CMOS errors) and the leaking planar battery.</ref>
This frees a stuck spindle for perhaps one boot. '''Image the drive immediately''' and replace it.


== References ==
== Common symptoms ==
ย 
* '''Click, then nothing''' โ€” a short on the planar or an adapter pulling the supply into fold-back before Power Good is asserted. Go to [[#Dead system|Dead system]].
* '''161 at every boot''' โ€” the battery. See [[#Battery|Battery]]. Replace with FRU 72X8498 or an equivalent CR-P2.
* '''165 at every boot''' โ€” run Auto Configuration from the Reference Diskette.
* '''Only part of the setup lost''' โ€” IBM's own note is that the battery is probably '''not''' the cause.<ref name="ard_batt" />
* '''Memory errors after a SIMM swap''' โ€” IBM's 2xx group for the wrong type or the wrong speed of module. Confirm the module against the machine's own specification rather than against a figure from a wiki page; this page previously quoted SIMM speeds for the Model 50 and the Model 50 Z that could not be sourced.
* '''Drive not detected''' โ€” ST-506 stiction, a badly seated ESDI cable, or dirty controller edge contacts.
* '''Random reboots under load''' โ€” check the line cord seating first, which is IBM's own first suggestion for unexpected resets, then the supply.<ref name="ard_err" />
* '''VGA showing wrong colours''' โ€” IBM's own discriminator for the 24xx codes is whether the colours change: if they do, suspect the display; if they do not, suspect the system board.<ref name="ard_err" />
ย 
== What has been removed from this page ==


<references />
* '''The ECA section.''' This page named ECA 087 and ECA 092 with model-specific meanings and attributed the affected serial-number ranges to an IBM HMM that is not hosted here. '''ECA 092 is verifiably something else''' โ€” the Ardent Tool of Capitalism documents it as the '''8570 Data Modification Patch''', a hardfile data-transfer patch for 25 MHz Model 70 machines with 80 MB or 160 MB hardfiles, not an ESDI adapter firmware update for the Model 50 Z.<ref name="ard_8570" /> ECA 087 could not be corroborated anywhere. Both have been removed rather than left to look like IBM data.
* '''The PSU wattage figure.''' No source was found for it.
* '''The SIMM access-time figures''' for the Model 50 and Model 50 Z.
* '''The Dallas DS12887 instruction''' โ€” see [[#Battery|Battery]].


== Related Pages ==
== Related pages ==


* [[IBM PS/2 Model 50]]
* [[IBM PS/2 Model 50]]
Line 294: Line 423:
* [[IBM PS/2 Model 50 Capacitor Replacement Guide]]
* [[IBM PS/2 Model 50 Capacitor Replacement Guide]]
* [[IBM PS/2 Model 60 Troubleshooting Guide]] โ€” tower sibling
* [[IBM PS/2 Model 60 Troubleshooting Guide]] โ€” tower sibling
* [[IBM PS/2 Model 70 Troubleshooting Guide]]
* [[IBM PS/2 Model 80 Troubleshooting Guide]]
* [[Capacitor Failure Symptoms]]
* [[Capacitor Failure Symptoms]]
* [[Recommended Tools]]


== References ==
== References ==


* [https://www.ardent-tool.com/trouble/ps2error.html PS/2 Error Codes], Ardent Tool of Capitalism. Authoritative reference for the complete 1xxโ€“25xx and 100xxโ€“112xx PS/2 numeric error code listing, the Power-Good-in-150-ms PSU spec, and the dead-system isolation procedure.
<references>
* [http://museodelcomputer.org/parts/ibm/ps2_50z/docs/error_codes.htm PS/2 Error Codes], Museodelcomputer.org. Reference for audio code patterns and minor code structure.
<ref name="ard_err">''PS/2 Error Codes'' and the linked error-code pages (100โ€“159, 160โ€“199, 200โ€“299, 300โ€“999, 1500โ€“2999, 10000โ€“11999), [https://www.ardent-tool.com/trouble/ps2error.html Ardent Tool of Capitalism]. A community reference that reproduces IBM's own symptom-and-FRU lists; content credited on the site to Louis F. Ohland, Peter H. Wendt, David L. Beem, William R. Walsh, Tatsuo Sunagawa, Tomรกลก Slavotรญnek, Jim Shorney, Tim N. Clarke, Kevin Bowling and others, and maintained by Tomรกลก Slavotรญnek. Source for the five beep-code patterns, the 4+4 eight-character error-code format and its abbreviation rules, every code and FRU/action entry in the tables on this page, the note that the 2xx minor-code-to-module decode applies only to the Models 56/57, 76/77, 85 and 90/95, the diagnostics procedure (cold-boot the Reference Diskette, diagnose the first error first, run Advanced Diagnostics before replacing FRUs, remove optional FRUs one at a time, external surge suppressors as a cause), and the complete dead-system procedure including the 150 ms Power Good requirement, the line-cord contact advice and the LogicLock note.</ref>
* [https://www.dosdays.co.uk/computers/IBM%20PS2%20Model%2050/ibm_ps2_model_50.php IBM PS/2 Model 50 โ€” DOS Days]. Reference for the ESDI controller architecture and SIMM-speed dependencies.
<ref name="ard_batt">''PS/2 RTC/CMOS Batteries'', [https://www.ardent-tool.com/misc/batteries.html Ardent Tool of Capitalism], based on content by Bob Eager and Peter H. Wendt. Source for the per-machine battery cross-reference (Model 50 and 50 Z: 6 V pack, FRU 72X8498; Models 25-286, 30-286, 35, 40, 55 SX, 55 LS, 65 SX: Dallas RTC module FRU 8509237; Models 56/57, 76/77, 90, 95 and others: 3 V coin cell FRU 33F8354), for the 6 V pack being a two-cell lithium camera battery with the CR-P2 / DL223A / EL223AP / K223LA / PC223 equivalents and its Battery/Speaker Assembly, for the Dallas module being a DS1287 replaceable by the DS12887 or DS12887+ but '''not''' the DS12C887, for the coin-cell service range of 2.5โ€“3.7 V and the note that low voltages can corrupt CMOS bits, and for the statement that a weak battery loses all of the setup information while a partial loss is probably not the battery.</ref>
* IBM, ''IBM Personal System/2 Hardware Maintenance Manual'' (S52G-9971-02, October 1994). Source for ECA 087 / 092 recalls and FRU listings.
<ref name="ard_8570">''8570 Type 3 & 4 Planar'', [https://www.ardent-tool.com/8570/Planar_T3-4.html Ardent Tool of Capitalism]. Source for ECA 092 being the 8570 Data Modification Patch, applying to 25 MHz 8570 systems with an 80 MB or 160 MB hardfile running DOS or OS/2, and for the other 8570 ECAs (021, 029) which are likewise 8570-specific.</ref>
* IBM, ''IBM Personal System/2 Model 50 Reference Diskette''. Source for SETUP, Auto Configuration, Advanced Diagnostics (Ctrl-A) and the ADF-based MCA card configuration.
</references>


{{Navbox-IBMComputers|state=collapsed}}
{{Navbox-IBMComputers|state=collapsed}}

Latest revision as of 10:31, 27 September 2026

IBM PS/2 Model 50. Source: Wikimedia Commons.

This guide covers diagnostics for the IBM PS/2 Model 50 (machine type 8550 โ€” the original 8550-021 and the 8550-031 / -061 Model 50 Z), and carries this wiki's reference copy of IBM's PS/2 numeric POST error code list, which the Model 60, 70 and 80 guides link to rather than repeat.

What changed here, and why it matters. An earlier version of this page carried a hand-transcribed error-code table in which a number of entries were PC/AT-era meanings applied to PS/2 codes, several codes did not exist in IBM's list at all, and the 161 entry told the reader to replace a Dallas DS12887 RTC module โ€” a part the Model 50 does not have. The tables below are transcribed from the Ardent Tool of Capitalism's error-code pages, which reproduce IBM's own symptom-and-FRU lists, and they keep IBM's FRU / action column, which is the part you can act on.[1]

POST beep codes

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These are IBM's PS/2 audio codes as published by the Ardent Tool of Capitalism. There are five of them, and three of the five mean the same thing.[1]

PS/2 beep codes (* = short beep, _ = long beep)
Pattern Meaning
* Normal operation
* * A problem exists โ€” check the configuration. Run diagnostics if no error code is displayed
_ * Display or display adapter problem
_ * * Display or display adapter problem
_ * * * Display or display adapter problem
* * * * * * (continuous short beeps) Check the keyboard
Continuous solid beep System board

Earlier versions of this page gave a longer beep table that assigned distinct meanings to the three long-plus-short patterns โ€” including an "EGA / advanced display" fault on machines with integrated VGA โ€” and added two rows ("click then no beep", "no display and no sound") that are not beep codes at all. Those have been removed. The two symptoms are real and are dealt with under Dead system below, which is where IBM's own procedure puts them.

Numeric POST error codes

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How to read the code. IBM's error messages are eight characters, in a 4 + 4 form: the first four digits are the major error code and the last two significant digits the minor (diagnostic) code, with trailing zeros to fill. The major code is largely the same as the PC/AT error codes. A message that appears as three, four or five characters is the same code abbreviated: add two zeros to the right and pad with zeros on the left to reach eight characters.[1]

IBM's own examples
Abbreviated Eight-character form
301 (codes 300โ€“999) 0003 0100
1701 (codes 1500โ€“2999) 0017 0100
16680 (codes 15000โ€“19999) 0166 8000

If a message appears as twelve characters, disregard the last four. The minor code depends on the error type and is mostly only specified when running Advanced Diagnostics, though it often appears at POST too; where the lists below show XX it means "don't care".[1]

Codes 100โ€“159 โ€” system board

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Error codes 100โ€“159, with IBM's FRU and action list
Code Symptom FRU / action
0001 01XX Interrupt failure. Possibly a bad battery or processor Run Advanced Diagnostics
0001 02XX ROM checksum or timer error. Possibly a bad battery or processor Run Advanced Diagnostics
0001 0300 Checksum or timer error Processor board, then system board
0001 02XX / 03XX / 04XX / 07XX โ€” System board, then processor board
0001 05XX Command not accepted Information only
0001 06XX Converting logic test failure Run Advanced Diagnostics
0001 07XX / 08XX / 09XX Interrupt or memory failure System board memory, system board, any adapter, bus adapter
0001 10XX Check memory Memory module kit, then system board
0001 11XX I/O channel check Adapter memory, expansion adapter, system board
0001 12XX / 13XX Possible Micro Channel timeout error. Often caused by a card with a defective MCA bus interface, or a card too slow to respond System board, processor board, any adapter
0001 14XX ROM error Any adapter, bus adapter
0001 15XX 80386 protected mode failure; BIOS checksum error System board
0001 16XX Possible read/write problem Run Advanced Diagnostics
0001 18XX Previously detected error System board memory, processor board
0001 19XX 2.88 MB diskette drive installed but not supported Run Automatic Configuration, then system board
0001 20XX Possible processor self-test failure Processor cache, processor board
0001 21XX Problem detected during memory remapping (256 KB ROM error) Information only
0001 22XX POST found a hardware error Run Advanced Diagnostics
0001 30XX POST could not start the operating system. Is the boot drive in the selectable drive sequence? Check the drive sequence
0001 3002 Drive startup sequence is corrupt or invalid Run Automatic Configuration and reset the sequence; if it persists, replace the system board
0001 3003 EEPROM could not be read Run Automatic Configuration; if it persists, replace the system board
0001 32XX DMA extended registers error Run Advanced Diagnostics
0001 33XX DMA verify function error โ€” logic failed Run Advanced Diagnostics
0001 34XX DMA arbitration logic error Run Advanced Diagnostics
0001 4908 / 4909 โ€” Check the cover lock and tamper-evident switches before replacing any FRU
0001 52XX Real time clock error. Not always a hardware failure Run Advanced Diagnostics
0001 56XX Security error โ€” covers removed without the key; tamper-evident switch tripped Reconfigure from the Reference Diskette; then the security switch assembly, then the system board

Note what is not in IBM's list: there is no 104 "protected mode failure" (that is 115), no 121 "unexpected hardware interrupt" (121 is a memory-remapping note and is information only), and no 151 at all.[1]

Codes 160โ€“199 โ€” configuration, battery and security

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Error codes 160โ€“199, with IBM's FRU and action list
Code Symptom FRU / action
0001 60XX System board ID not recognised. Possible system board failure Run Advanced Diagnostics
0001 61XX Battery. IBM's own caution: the lithium battery presents a fire, explosion or severe burn risk, and using another battery could cause ignition or explosion Battery, then complex, system board, bus adapter
0001 62XX Be sure all devices are powered on. Check enable/disable settings. Configuration changed? Run Automatic Configuration Any device, then battery
0001 63XX Date and time error Set the date and time
0001 6000 / 6400 / 6500 / 6700 / 6900 If setting configuration, date and time does not solve it, check the devices list Set configuration and features, then system board
0001 66XX Adapter busy. Reseat all adapters Run Advanced Diagnostics
0001 67XX Clock is not working correctly Set features; set date and time
0001 68XX Real time clock error. This is not always a hardware failure Run Advanced Diagnostics
0001 69XX Processor configuration error Run Automatic Configuration and verify the processor configuration before replacing FRUs
0001 70XX ASCII console setup conflict โ€” the serial port is disabled From Set Configuration, Change Configuration, enable the port
0001 73XX Possibly a weak battery; bad CMOS/NVRAM checksum Set configuration / features
0001 74XX If the configuration has changed run Automatic Configuration, otherwise Advanced Diagnostics Any device, system board, bus adapter
0001 75XX Security error โ€” the system board EEPROM failed System board
0001 76XX Security error โ€” covers removed without the key Reconfigure, then security switch assembly, then system board
0001 77XX / 78XX Security error โ€” passwords corrupted. Reset passwords System board
0001 79XX System error log might be full Read and note the errors, clear the log, then run Advanced Diagnostics
0001 81XX The machine needs a network adapter for remote IPL, or a hard disk with ID LUN 0 for IML; neither was detected Run Automatic Configuration, then network adapter, hard disk, system board
0001 82XX Privileged access password data is corrupted Information only โ€” move jumper JMP2 to position 0, write enabled, to restore it
0001 83XX Wrong password entered Enter the privileged access password, not the power-on password
0001 84XX Power-on password corrupted The user must reset the password
0001 85XX Selectable startup sequence corrupted Run the Select Startup Sequence utility
0001 86XX Security error, hardware failed Run Advanced Diagnostics, then system board
0001 87XX Vital Product Data error โ€” system serial number corrupted Set system identification and retype the serial number; if it persists, suspect the system board
0001 88XX Vital Product Data error Run Automatic Configuration
0001 89XX The wrong password was entered three times Information only โ€” clear the system error log and restart
0001 91XX 82385 cache test failed Run Advanced Diagnostics
0001 99XX User indicated the configuration is invalid System board
0001 XXXX (not listed) โ€” Planar / complex, any adapter, bus adapter

The 161 entry is a battery entry, not an RTC-module entry. See Battery below for which battery this machine actually takes.

162 is not a checksum error. IBM's 162 tells you to check that devices are powered on and that the configuration has not changed; the bad-checksum code is 0001 73XX, and IBM's note there is "possibly a weak battery".[1]

Codes 200โ€“299 โ€” memory

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Error codes 200โ€“299, with IBM's FRU and action list
Code Symptom FRU / action
0002 01XX / 05XX Reseat system board memory System board memory, then system board
0002 0XXY / 17XY Memory failure System board memory, memory riser card, processor board; then system board
0002 10XX / 11XX Check memory Processor board, system board memory, memory riser card, system board
0002 11CZ Missing or unsupported memory module โ€” none installed, or one that does not provide the required presence-detect coding Memory module, system board
0002 15UZ No system memory is installed Memory module, system board
0002 14XX / 15XX / 16XX / 21XX / 26XX / 35XX / 40XX / 41XX Check memory. It might be the wrong type or the wrong speed System board memory, memory riser card; then system board, processor board; then bus adapter
0002 21XX ROM to RAM parity error System board
0002 35XX Single-bit (correctable) ECC memory error Processor / system board, then system board memory
0002 51XX Memory location changed on the memory expansion option Information only
0002 55XX Check memory System board memory, then system board
0002 9000 Unsupported memory combination detected Correct the combination of ECC and parity modules, run Automatic Configuration, rerun Advanced Diagnostics
0002 91XXโ€“94XX, 9800 Checksum value mismatch Run Automatic Configuration, then rerun Advanced Diagnostics
0002 95XX / 96XX Check memory for an unsupported configuration or modules System board memory

The "last two digits identify the failing module" rule applies only to the Models 56/57, 76/77, 85 and 90/95.[1] On the earlier machines the 2xx minor code does not decode to a socket, and the PC/AT-era reading in which the digits before "201" identify a failing 64 KB bank and bit is not the PS/2 behaviour. Earlier versions of this page said otherwise.

Codes 300โ€“999 โ€” keyboard, ports, display, diskette, coprocessor

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Error codes 300โ€“999, with IBM's FRU and action list
Code Symptom FRU / action
0003 01XX / 02XX โ€” Keyboard cable, then system board
0003 03XX / 04XX โ€” System board, keyboard, keyboard cable
0003 05XX Keyboard voltage error Keyboard port fuse, keyboard cable, system board. If there is no fuse in the system, replace the system board
0003 06XX Unsupported keyboard attached Check for an unsupported keyboard
0003 07XX โ€” Keyboard, keyboard cable
0003 20XX โ€” System board
0004 01XX โ€” System board. On the 90/95 this is a parallel port error, not a video error
0004 02XXโ€“05XX โ€” System board
0005 XXXX โ€” Display adapter, any type
0006 01XX โ€” Defective diskette, diskette drive, system board
0006 02XX Invalid boot record Defective diskette
0006 04XX Unsupported drive or cable โ€” the drive must be a media-sense type Diskette drive, system board, diskette drive cable
0006 05XX Diskette drive error Run Advanced Diagnostics
0006 06XXโ€“60XX (most) Generally media errors. Try a known-good diskette; if the error returns, replace the drive Diskette, diskette drive, system board
0006 62XX Wrong drive type installed Information only
0006 63XX Wrong media type in the drive Information only
0007 XXXX Math coprocessor. For a 486 processor, erase COPROC.DGS from the backup Reference Diskette, restore the system partition from the corrected backup, and rerun Advanced Diagnostics Math coprocessor, then system board

The math coprocessor family is 7xx, not 8xx.[1] Earlier versions of several pages in this family headed it "8xx โ€” Math Coprocessor" with a single "801" code. In IBM's list 0008 does not exist and 0018 XXXX is the system board expansion unit.

401 is not a video code on the machines where IBM annotates it โ€” it is a parallel port error on the 90/95 and otherwise a system board FRU. The general display-adapter family is 0005 XXXX.[1]

Codes 1500โ€“2999 โ€” ST-506 fixed disk and video

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Error codes 1500โ€“2999 (selected), with IBM's FRU and action list
Code Symptom FRU / action
0017 01XX / 03XX / 04XX / 14XX, and any 0017 XXXX not listed below โ€” ST-506 hard disk drive, cable, adapter; then system board; then power supply
0017 02XX โ€” ST-506 hard disk adapter
0017 05XXโ€“91XX (most) Read/write problem. Confirm the drive type is supported; if it is, try a low-level format; if the error continues, replace the drive Format the drive, then the drive
0018 0100โ€“0700 โ€” System board
0018 6XXX โ€” Set configuration / features, then battery
0018 XXXX (not listed) โ€” System board expansion unit
0024 0100 / 0200 If the screen colours change Display, any type
0024 0100 / 0200 If the screen colours are correct System board, then display
0024 0900 โ€” Display, any type
0024 1000 โ€” System board

There is no 2403 or 2408 in IBM's list. The 24xx family is four entries, and IBM's own discriminator for two of them is whether the screen colours change.[1]

Codes 10400โ€“10499 โ€” ESDI fixed disk

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This is the family most often reproduced wrongly. IBM's list is not a consecutive run of codes, and several codes that circulate widely are not in it at all.

ESDI error codes, with IBM's FRU and action list
Code Symptom FRU / action
0104 50XX / 51XX / 90XX / 91XX / 92XX / 99XX ESDI read/write error Run Advanced Diagnostics, riser card if installed, ESDI drive, system board
0104 52XX ESDI seek test error Run Advanced Diagnostics
0104 53XX ESDI โ€” wrong drive type? Information only
0104 54XX ESDI sector buffer test error Run Advanced Diagnostics
0104 55XX / 56XX ESDI controller error Run Advanced Diagnostics
0104 59XX ESDI drive diagnostic command error Information only
0104 61XX ESDI drive format error Run Advanced Diagnostics
0104 62XX ESDI controller seek error Run Advanced Diagnostics
0104 64XX ESDI hard disk read error Run Advanced Diagnostics
0104 67XX ESDI drive non-fatal seek error Run Advanced Diagnostics
0104 68XX ESDI drive fatal seek error Run Advanced Diagnostics
0104 69XX ESDI drive soft error count exceeded Run Advanced Diagnostics
0104 70XX / 71XX / 72XX ESDI controller wrap error Run Advanced Diagnostics
0104 73XX ESDI corrupt data. A low-level format might be required Information only
0104 80XX โ€” ESDI drive, drive cable, ESDI controller, system board, riser card (Models 50, 55, 70 where applicable)
0104 81XX ESDI drive D seek error Run Advanced Diagnostics
0104 82XX ESDI drive select acknowledgement bad Run Advanced Diagnostics

Codes that are not in IBM's list and have been removed from this wiki: 10463, 10465, 10466, 10484, 10485, 10486, 10487, 10488, 10489 and 10493. Codes whose meaning was wrong: 10462 (controller seek, not a controller-side read failure), 10464 (hard disk read error, not a boot-record failure), 10470/10471/10472 (all three are controller wrap errors, not drive timeout, drive busy and status error), 10473 (corrupt data, not a read-verify error) and 10482 (drive select acknowledgement, not controller failure). Code 10459 was missing.

Other families

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IBM's full listing runs to 29999 and includes adapter-specific families โ€” 0037 XXXX SCSI on the system board, 0074 XXXX 8514/A, 0075 XXXX XGA and display adapters, 0086 XXXX pointing device, 0096 XXXX SCSI adapter with cache, and more. It also has separate IML (I999xxxx / 0999xxxx) and SCSI (RDDDPLSCB QEET) code schemes. Consult the Ardent Tool of Capitalism's error-code pages for these rather than a per-machine summary.[1]

Diagnostics procedure

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IBM's own procedural notes, which change the order of work:[1]

  • Cold-boot the Reference Diskette โ€” power on with the diskette already in the drive. Soft-booting it can produce false errors and a false indication that a power-on password is already set.
  • If several errors appear, diagnose the first one first. The cause of the first can cause other devices to fail. This matters most with configuration errors.
  • Always cold boot and run Advanced Diagnostics (System Programs, then Ctrl-A at the main menu) before replacing components. If the diagnostics do not fail, replacing parts probably will not help โ€” look at the software instead.
  • If an adapter consists of several FRUs, remove the optional FRUs one at a time to see whether the symptoms change, before replacing the adapter.
  • External surge suppressors are a documented source of hard-to-diagnose problems.

Dead system

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No POST, blank screen, no beep. IBM's stated most likely cause is a device shorting out the power supply โ€” an improperly inserted memory module, a defective adapter or a defective device. The system board must present a Power Good signal to the power supply within 150 ms or the supply shuts itself down internally. That is the mechanism behind the "click and then nothing" symptom.[1]

IBM's list of the usual causes is blunt: a SIMM inserted backwards, an adapter not fully seated, the power cord not plugged in, an unsupported or defective adapter, or โ€” on a heavily loaded machine โ€” too many drives trying to spin up at once, which can be fixed by leaving the motor-start jumper open so the drives start after the controller interrogates them.[1]

The procedure:[1]

  1. Check the line cord at both ends. IBM singles this out: intermittent and very hard to diagnose faults, including unexpected power-on resets during operation, are caused by line cords that are not fully seated or are too loose to make a tight connection. Slightly forming the male contacts in the power supply connector may fix it, or the female contacts in the plug. Remove the cord from the outlet before working on its contacts. Replacing the cord is sometimes necessary.
  2. Remove all adapters, options and extra memory.
  3. Remove all external connections โ€” keyboard, mouse, display.
  4. Plug in, power on, and listen for a beep. A beep means POST has run; several beeps may occur.
  5. If no beep: verify continuity through the speaker. If the speaker is good, replace the system board memory and retry. If there is still no beep, measure the power supply voltages โ€” if they are correct, replace the system board; if they are wrong, replace the power supply.
  6. If a beep occurs: reinstall the adapters one at a time, retrying after each. When the beep stops, the last item fitted is the suspect. There is no need to reconfigure between steps, because all you are looking for is the beep.

On machines with LogicLock, the switches that detect unauthorised access can be left in the wrong position when the case is reassembled, which produces a machine that appears dead or will not run with the cover removed.[1]

Battery

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Defective or weak batteries can cause the loss of all setup information. If only part of the setup is lost, the battery is probably NOT the cause. Inaccurate time is usually software, though some older models with 6 V batteries are prone to the clock running slow.[2]

The Model 50 and Model 50 Z take a 6 V lithium battery pack, IBM FRU P/N 72X8498 โ€” a two-cell pack, usually yellow with black ends, held in a dedicated Battery/Speaker Assembly. It is a camera battery: equivalents are the CR-P2 (Varta, Panasonic, GP, Sony, Sanyo), DL223A (Duracell), EL223AP (Ever Ready), K223LA (Kodak) and PC223 (Ray-O-Vac).[2]

There is no Dallas RTC module on a Model 50. The Dallas self-contained module (IBM FRU 8509237, Dallas DS1287) is fitted to the Models 25-286, 30-286, 35, 40, 55 SX and 55 LS and 65 SX โ€” not to the 50, 50 Z, 60, 70, 80, P70 or P75, which all use the 6 V pack.[2]

If you are working on a machine that does take the Dallas module, two things are worth knowing: the DS1287 can be replaced by the pin-compatible DS12887 (or DS12887+, the lead-free version), but do not use the DS12C887 โ€” it uses the century byte differently and will not work in a PS/2.[2]

165 card ID mismatch

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The most common POST error on a Model 50 with any MCA cards fitted. It occurs when a card has been added or removed since the last Automatic Configuration run, when an ADF (Adapter Definition File) is missing from the working Reference Diskette, or when a card's edge fingers are dirty enough that it reports a different ID intermittently.

To clear it: boot the Reference Diskette, back it up to a working diskette if you have not already, then Set Configuration โ†’ Run Auto Configuration, inserting each option diskette as prompted to load the missing ADFs. Copy the ADF for each MCA card onto your working Reference Diskette before fitting the card.

Reference Diskette and Advanced Diagnostics

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The Model 50 has no built-in SETUP โ€” all configuration is done from the Model 50 Reference Diskette.

  1. Always cold-boot it (insert before powering on). Warm-booting can report false errors and falsely indicate that a power-on password is set.[1]
  2. Back the Reference Diskette up to a working diskette on first use. The original is read-only.
  3. Set Configuration โ†’ View configuration shows the current state.
  4. Set Configuration โ†’ Run Auto Configuration runs MCA card detection and ADF lookup.
  5. Test the computer โ†’ Diagnostics runs the hardware test suite.
  6. Ctrl-A from the main menu enters Advanced Diagnostics, which produces the minor codes.

ESDI drive stiction recovery (8550-061)

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If the 60 MB ESDI drive does not spin up:

  1. Power off and remove the drive from its caddy.
  2. Hold it horizontal and rotate it gently around the spindle axis.
  3. Refit and power on.

This frees a stuck spindle for perhaps one boot. Image the drive immediately and replace it.

Common symptoms

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  • Click, then nothing โ€” a short on the planar or an adapter pulling the supply into fold-back before Power Good is asserted. Go to Dead system.
  • 161 at every boot โ€” the battery. See Battery. Replace with FRU 72X8498 or an equivalent CR-P2.
  • 165 at every boot โ€” run Auto Configuration from the Reference Diskette.
  • Only part of the setup lost โ€” IBM's own note is that the battery is probably not the cause.[2]
  • Memory errors after a SIMM swap โ€” IBM's 2xx group for the wrong type or the wrong speed of module. Confirm the module against the machine's own specification rather than against a figure from a wiki page; this page previously quoted SIMM speeds for the Model 50 and the Model 50 Z that could not be sourced.
  • Drive not detected โ€” ST-506 stiction, a badly seated ESDI cable, or dirty controller edge contacts.
  • Random reboots under load โ€” check the line cord seating first, which is IBM's own first suggestion for unexpected resets, then the supply.[1]
  • VGA showing wrong colours โ€” IBM's own discriminator for the 24xx codes is whether the colours change: if they do, suspect the display; if they do not, suspect the system board.[1]

What has been removed from this page

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  • The ECA section. This page named ECA 087 and ECA 092 with model-specific meanings and attributed the affected serial-number ranges to an IBM HMM that is not hosted here. ECA 092 is verifiably something else โ€” the Ardent Tool of Capitalism documents it as the 8570 Data Modification Patch, a hardfile data-transfer patch for 25 MHz Model 70 machines with 80 MB or 160 MB hardfiles, not an ESDI adapter firmware update for the Model 50 Z.[3] ECA 087 could not be corroborated anywhere. Both have been removed rather than left to look like IBM data.
  • The PSU wattage figure. No source was found for it.
  • The SIMM access-time figures for the Model 50 and Model 50 Z.
  • The Dallas DS12887 instruction โ€” see Battery.
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References

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  1. โ†‘ 1.00 1.01 1.02 1.03 1.04 1.05 1.06 1.07 1.08 1.09 1.10 1.11 1.12 1.13 1.14 1.15 1.16 1.17 1.18 PS/2 Error Codes and the linked error-code pages (100โ€“159, 160โ€“199, 200โ€“299, 300โ€“999, 1500โ€“2999, 10000โ€“11999), Ardent Tool of Capitalism. A community reference that reproduces IBM's own symptom-and-FRU lists; content credited on the site to Louis F. Ohland, Peter H. Wendt, David L. Beem, William R. Walsh, Tatsuo Sunagawa, Tomรกลก Slavotรญnek, Jim Shorney, Tim N. Clarke, Kevin Bowling and others, and maintained by Tomรกลก Slavotรญnek. Source for the five beep-code patterns, the 4+4 eight-character error-code format and its abbreviation rules, every code and FRU/action entry in the tables on this page, the note that the 2xx minor-code-to-module decode applies only to the Models 56/57, 76/77, 85 and 90/95, the diagnostics procedure (cold-boot the Reference Diskette, diagnose the first error first, run Advanced Diagnostics before replacing FRUs, remove optional FRUs one at a time, external surge suppressors as a cause), and the complete dead-system procedure including the 150 ms Power Good requirement, the line-cord contact advice and the LogicLock note.
  2. โ†‘ 2.0 2.1 2.2 2.3 2.4 PS/2 RTC/CMOS Batteries, Ardent Tool of Capitalism, based on content by Bob Eager and Peter H. Wendt. Source for the per-machine battery cross-reference (Model 50 and 50 Z: 6 V pack, FRU 72X8498; Models 25-286, 30-286, 35, 40, 55 SX, 55 LS, 65 SX: Dallas RTC module FRU 8509237; Models 56/57, 76/77, 90, 95 and others: 3 V coin cell FRU 33F8354), for the 6 V pack being a two-cell lithium camera battery with the CR-P2 / DL223A / EL223AP / K223LA / PC223 equivalents and its Battery/Speaker Assembly, for the Dallas module being a DS1287 replaceable by the DS12887 or DS12887+ but not the DS12C887, for the coin-cell service range of 2.5โ€“3.7 V and the note that low voltages can corrupt CMOS bits, and for the statement that a weak battery loses all of the setup information while a partial loss is probably not the battery.
  3. โ†‘ 8570 Type 3 & 4 Planar, Ardent Tool of Capitalism. Source for ECA 092 being the 8570 Data Modification Patch, applying to 25 MHz 8570 systems with an 80 MB or 160 MB hardfile running DOS or OS/2, and for the other 8570 ECAs (021, 029) which are likewise 8570-specific.


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