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Cite Apple's ImageWriter II Service Source inline at the 26LS30 fault, so the printer can be ruled out before a line driver is desoldered
 
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| manufacturer = Apple Computer, Inc.
| manufacturer = Apple Computer, Inc.
| type        = Personal computer
| type        = Personal computer
| release_date = September 10, 1984
| release_date = September 1984
| discontinued = April 14, 1986
| discontinued = April 1986
| price        = US$3,195
| price        = US$3,195
| cpu          = Motorola 68000 @ 7.83 MHz
| cpu          = Motorola 68000 @ 7.83 MHz
| memory      = 512 KB RAM (not expandable)
| memory      = 512 KB, soldered, not user-expandable
| storage      = 400 KB 3.5″ floppy drive
| rom          = 64 KB
| display      = 9″ monochrome CRT (512 × 342 px)
| storage      = Internal single-sided 400 KB 3.5-inch floppy drive
| sound        = Monaural 8‑bit, 22 kHz (4‑voice)
| display      = 9-inch monochrome CRT, 512 × 342 pixels
| dimensions  = 13.6″ H × 9.6″ W × 10.9″ D
| sound        = Four-voice, 8-bit D/A conversion, 22 kHz sampling
| weight      = 16.5 lb (7.5 kg)
| ports        = DB-19 external floppy; DE-9 mouse; RJ-11 keyboard; 2 × RS-232/RS-422 serial (DE-9)
| os          = System 1.0 – System 4.1
| power        = 105–125 V AC, 50–60 Hz, 60 W maximum
| predecessor  = [[Macintosh 128K]]
| dimensions  = 13.6 in H × 9.6 in W × 10.9 in D (34.5 × 24.4 × 27.6 cm)
| successor    = [[Macintosh 512Ke]]
| weight      = 16 lb 8 oz (7.5 kg)
| codename    = Engine, Hero
| os          = System 1.1 – System 4.1
| predecessor  = [[Macintosh 128K]]
| successor    = [[Macintosh 512Ke]]
| codename    = Fat Mac
| model        = M0001W
| model        = M0001W
}}The '''Macintosh 512K''', released on '''September 10, 1984''', was an improved version of the [[Macintosh 128K]]. It featured '''four times the RAM (512 KB)''', allowing for improved multitasking and compatibility with a wider range of software. It retained the same '''Motorola 68000 processor running at 7.83 MHz''' and the '''9-inch monochrome display''' with a '''400 KB floppy disk drive'''.
}}
The '''Macintosh 512K''' was introduced in September 1984 as a [[Macintosh 128K]] with four times the memory. Everything else — the 68000 processor, the 64 KB ROM, the 9-inch monochrome screen and the single-sided 400 KB floppy drive — is the same, and Apple services the two machines from a single manual.<ref name="ss128">Apple Computer, ''Macintosh 128K/512K Service Source'' — Specifications, Take Apart and Adjustments chapters. Hosted on this wiki: [[:File:Macintosh 128k.512k.pdf]].</ref> It sold for US$3,195 and was nicknamed the Fat Mac.<ref name="ah">apple-history.com, ''Macintosh 512K'' (secondary source, used for the introduction price, codename and market dates).</ref>


Due to its increased memory, the Macintosh 512K could run more advanced applications, including '''MacDraw''', '''MacProject''', and '''Microsoft Multiplan'''. However, it still lacked built-in support for an internal hard drive, relying on external floppy drives for additional storage. The 512K model was succeeded by the [[Macintosh Plus]], which introduced '''expandable RAM and an external SCSI port'''.
The extra memory made the machine usable with the larger applications of the period, but it still had no internal hard disk, no SCSI port and no memory expansion: the RAM is soldered down. The [[Macintosh Plus]] addressed all three.


== Maintenance ==
== Maintenance ==
Due to the 512K's similarities with the 128K, there is no difference in it's maintenance, PCB or Schmatics, please see the [[Macintosh 128K]] page for maintenance, guides and more information.


== Technical Details ==
The 512K is mechanically and electrically the same machine as the 128K, so its servicing, board layout and schematics are shared. See '''[[Macintosh 128K/512K General Maintenance]]''' and the [[Macintosh 128K]] page.
 
The machine contains a CRT; read [[CRT Discharge Procedure]] before opening the case.
 
== Specifications ==
 
Every figure in this table is from Apple's own specification pages for the 128K/512K.<ref name="ss128" />
 
<templatestyles src="Template:StyledTable/styles.css" />
<templatestyles src="Template:StyledTable/styles.css" />
 
{| class="wikitable styled-table" style="width:80%;"
=== System Architecture at a Glance ===
! Item !! Specification
{| class="wikitable styled-table" style="width:70%; text-align:center;"
|-
! Sub-system !! Specification
| CPU || Motorola 68000, 7.83 MHz
|-
| RAM || 512 KB (the same manual covers the 128 KB machine)
|-
|-
| '''CPU''' || Motorola 68000 @ 7.8336 MHz  (15.667 MHz ÷ 2) 
| ROM || 64 KB
|-
|-
| '''Bus width''' || 16-bit data • 24-bit address (16 MB logical space) 
| PRAM || CMOS custom chip with 256 bytes of parameter memory, backed by a 4.5 V user-replaceable battery
|-
|-
| '''ROM''' || 64 KB “Boot/Toolbox” (4 × 16 KB HN462716 mask ROMs) 
| Floppy drive || Internal single-sided 3.5-inch drive, 400 KB
|-
|-
| '''RAM''' || 512 KB DRAM (16 × 256-Kbit 150 ns) – *soldered, non-expandable* 
| External floppy || DB-19 connector
|-
|-
| '''Video''' || 512 × 342 monochrome frame-buffer (22.1 KB) DMA-shared with system RAM 
| Mouse || DE-9 connector; mechanical tracking, optical shaft encoding at 3.54 pulses per mm
|-
|-
| '''Sound''' || 8-bit PWM DAC via VIA timers • 22 kHz low-pass to speaker / 3.5 mm jack 
| Keyboard || 58 keys, software mapped, RJ-11 connector
|-
|-
| '''Disk I/O''' || Sony OA-D34V 400 KB GCR 3.5″ drive • IWM controller 
| Serial || Two RS-232/RS-422 ports, DE-9 connectors
|-
|-
| '''Ports''' || DE-9 mouse/KB • DB-19 ext. floppy • RS-422 serial × 2 (230 kbps) • 3/8″ audio-out 
| Sound || Four-voice, 8-bit digital/analogue conversion, 22 kHz sampling rate
|}
 
=== Memory Map (Physical) ===
{| class="wikitable styled-table" style="width:70%; text-align:center;"
|+'''Macintosh 512K Address Space'''
! Range !! Size !! Purpose
|-
|-
| $000000 – $07FFFF || 512 KB || '''DRAM''' (program, frame-buffer, stack, heap)
| Video || 9-inch diagonal screen, 512 × 342 bit-mapped display
|-
|-
| $400000 – $41FFFF || 128 KB || '''ROM''' (Boot + Toolbox)
| Line voltage || 105–125 V AC, 50–60 Hz
|-
|-
| $480000 – $4BFFFF || 256 KB || '''I/O space''' (VIA 1 & 2, SCC, IWM, VBL PAL)
| Maximum power || 60 W
|-
|-
| $500000 – $5FFFFF || 1 MB || '''Reserved / not decoded'''
| Dimensions || 13.6 × 9.6 × 10.9 in (34.5 × 24.4 × 27.6 cm)
|-
|-
| $600000 – $FFFFFF || Mirrors / “ghost ranges”
| Weight || 16 lb 8 oz (7.5 kg)
|}
|}


*Frame-buffer note:* display memory occupies '''$07B000 – $07FFFF''' (22,016 bytes). 
== Memory ==
DMA steals cycles from the 68000 only during active scan-lines, identical to the 128 K.


=== ROM Layout (64 KB) ===
The 512 KB is soldered to the logic board. Apple offered no memory upgrade for this machine, and the RAM configuration is fixed in the logic that decodes it; period third-party boards that fitted Macintosh Plus ROMs and more memory existed, but they are logic board modifications rather than upgrades.<ref name="ah" /> The Macintosh Plus, which introduced the four 30-pin SIMM sockets used across the rest of the compact family, is documented on the [[Macintosh Plus Memory Upgrade Guide]].
{| class="wikitable styled-table" style="width:80%;"
 
! Offset !! Size !! Module (v3.3 ROM set)
== Power rails ==
|-
| $400000 || 8 KB || 68000 vectors + mini-shell
|-
| $402000 || 16 KB || QuickDraw 1.0 (mono)
|-
| $406000 || 20 KB || Macintosh Toolbox routines
|-
| $40B000 || 12 KB || SANE (IEEE fp) + traps
|-
| $40E000 || 8 KB || Sony IWM floppy driver / boot
|}


=== Video Timing ===
Unlike the later compacts, this generation '''does''' have a published voltage adjustment. Apple's procedure connects the Macintosh voltage test cable (part number 077-0135) to the external floppy port and adjusts the regulator on the power/sweep board for '''11.90–12.75 V''' on the orange lead and '''4.85–5.15 V''' on the red lead; if both cannot be brought inside those windows the board is replaced.<ref name="ss128" /> The full procedure, with its warnings, is written up on [[Macintosh Plus General Maintenance]], which uses the same board family.
{| class="wikitable styled-table" style="width:60%; text-align:center;"
! Parameter !! Value (NTSC)
|-
| Pixel clock || 7.833 MHz 
|-
| Horizontal total || 704 px (512 active) 
|-
| Vertical total || 370 lines (342 active)
|-
| Refresh rate || 60.15 Hz 
|}


=== Floppy-Disk Format ===
== Known board-level faults ==
* 80 tracks • single-sided variable-speed GCR 
* 12 sectors/track (outer) → 8 sectors/track (inner) 
* 512-byte sectors • 400 KB formatted capacity


=== Key I/O ICs ===
''The Dead Mac Scrolls'' documents two faults that present as software problems:<ref name="dms">Larry Pina, ''The Dead Mac Scrolls'', Peachpit Press, 1992, "Early Macs" chapter. Hosted on this wiki: [[:File:The Dead Mac Scrolls 1992.pdf]].</ref>
* '''6522 VIA × 2''' – system timers, sound PWM, keyboard/mouse handshake 
* A 512K or 512Ke that resets a directly connected ImageWriter II on the printer port, or that never appears on an AppleTalk network, usually has a failed '''26LS30''' line driver at board location '''B6'''. Before replacing it, rule out the printer: Apple's own '''[[ImageWriter II Service Source]]''' carries the Quick Problems and Carriage Movement symptom charts, and a self-test on the printer separates a printer fault from a line-driver fault without desoldering anything. That volume is partial by Apple's design — it has no Take Apart chapter, no parts list and no exploded view.
* '''8530 SCC''' – dual RS-422 serial ports 
* On an original 128K analogue board that has been paired with an upgraded logic board, repeatable system errors that no other Macintosh shows are a low +5 V rail; the overvoltage reference diode (1N5349B) at '''CR18''' is the part to check.
* '''IWM''' – “Integrated Woz Machine” floppy controller 
* '''MC6883 PAL''' – VBL interrupt generator & DRAM time-slot arbiter


=== Sound Path ===
== Related pages ==
The 68000 writes 8-bit samples to VIA Port A. VIA Timer 1 toggles Port B at 22.254 kHz, producing pulse-width-modulated audio → RC filter → LM380 amplifier → speaker/headphone jack.
* [[Macintosh 128K]]
* [[Macintosh 512Ke]]
* [[Macintosh Plus]]
* [[Macintosh 128K/512K General Maintenance]]
* [[Sad Mac Error Codes]] and the [[Sad Mac Decoder]]
* [[CRT Discharge Procedure]]


=== Hardware Easter Egg ===
== References ==
*Hold* '''⌘ + ⌥ + ⇧ + Clear''' at boot to hear the hidden “bass” startup chime. 
<references />
(The 512K retains this ROM routine; it was removed in the 512Ke/Plus.)


[[Category:Apple Vintage Computers]]
[[Category:Apple Vintage Computers]]


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

Latest revision as of 02:32, 25 September 2026

Macintosh 512K
Specifications
ManufacturerApple Computer, Inc.
TypePersonal computer
ReleasedSeptember 1984
DiscontinuedApril 1986
Intro priceUS$3,195
CPUMotorola 68000 @ 7.83 MHz
Memory512 KB, soldered, not user-expandable
StorageInternal single-sided 400 KB 3.5-inch floppy drive
Display9-inch monochrome CRT, 512 × 342 pixels
SoundFour-voice, 8-bit D/A conversion, 22 kHz sampling
ROM64 KB
Ports / interfaceDB-19 external floppy; DE-9 mouse; RJ-11 keyboard; 2 × RS-232/RS-422 serial (DE-9)
Power105–125 V AC, 50–60 Hz, 60 W maximum
Dimensions13.6 in H × 9.6 in W × 10.9 in D (34.5 × 24.4 × 27.6 cm)
Weight16 lb 8 oz (7.5 kg)
OS / FirmwareSystem 1.1 – System 4.1
PredecessorMacintosh 128K
SuccessorMacintosh 512Ke
CodenameFat Mac
Model no.M0001W

The Macintosh 512K was introduced in September 1984 as a Macintosh 128K with four times the memory. Everything else — the 68000 processor, the 64 KB ROM, the 9-inch monochrome screen and the single-sided 400 KB floppy drive — is the same, and Apple services the two machines from a single manual.[1] It sold for US$3,195 and was nicknamed the Fat Mac.[2]

The extra memory made the machine usable with the larger applications of the period, but it still had no internal hard disk, no SCSI port and no memory expansion: the RAM is soldered down. The Macintosh Plus addressed all three.

Maintenance

[edit | edit source]

The 512K is mechanically and electrically the same machine as the 128K, so its servicing, board layout and schematics are shared. See Macintosh 128K/512K General Maintenance and the Macintosh 128K page.

The machine contains a CRT; read CRT Discharge Procedure before opening the case.

Specifications

[edit | edit source]

Every figure in this table is from Apple's own specification pages for the 128K/512K.[1]

Item Specification
CPU Motorola 68000, 7.83 MHz
RAM 512 KB (the same manual covers the 128 KB machine)
ROM 64 KB
PRAM CMOS custom chip with 256 bytes of parameter memory, backed by a 4.5 V user-replaceable battery
Floppy drive Internal single-sided 3.5-inch drive, 400 KB
External floppy DB-19 connector
Mouse DE-9 connector; mechanical tracking, optical shaft encoding at 3.54 pulses per mm
Keyboard 58 keys, software mapped, RJ-11 connector
Serial Two RS-232/RS-422 ports, DE-9 connectors
Sound Four-voice, 8-bit digital/analogue conversion, 22 kHz sampling rate
Video 9-inch diagonal screen, 512 × 342 bit-mapped display
Line voltage 105–125 V AC, 50–60 Hz
Maximum power 60 W
Dimensions 13.6 × 9.6 × 10.9 in (34.5 × 24.4 × 27.6 cm)
Weight 16 lb 8 oz (7.5 kg)

Memory

[edit | edit source]

The 512 KB is soldered to the logic board. Apple offered no memory upgrade for this machine, and the RAM configuration is fixed in the logic that decodes it; period third-party boards that fitted Macintosh Plus ROMs and more memory existed, but they are logic board modifications rather than upgrades.[2] The Macintosh Plus, which introduced the four 30-pin SIMM sockets used across the rest of the compact family, is documented on the Macintosh Plus Memory Upgrade Guide.

Power rails

[edit | edit source]

Unlike the later compacts, this generation does have a published voltage adjustment. Apple's procedure connects the Macintosh voltage test cable (part number 077-0135) to the external floppy port and adjusts the regulator on the power/sweep board for 11.90–12.75 V on the orange lead and 4.85–5.15 V on the red lead; if both cannot be brought inside those windows the board is replaced.[1] The full procedure, with its warnings, is written up on Macintosh Plus General Maintenance, which uses the same board family.

Known board-level faults

[edit | edit source]

The Dead Mac Scrolls documents two faults that present as software problems:[3]

  • A 512K or 512Ke that resets a directly connected ImageWriter II on the printer port, or that never appears on an AppleTalk network, usually has a failed 26LS30 line driver at board location B6. Before replacing it, rule out the printer: Apple's own ImageWriter II Service Source carries the Quick Problems and Carriage Movement symptom charts, and a self-test on the printer separates a printer fault from a line-driver fault without desoldering anything. That volume is partial by Apple's design — it has no Take Apart chapter, no parts list and no exploded view.
  • On an original 128K analogue board that has been paired with an upgraded logic board, repeatable system errors that no other Macintosh shows are a low +5 V rail; the overvoltage reference diode (1N5349B) at CR18 is the part to check.
[edit | edit source]

References

[edit | edit source]
  1. ↑ 1.0 1.1 1.2 Apple Computer, Macintosh 128K/512K Service Source — Specifications, Take Apart and Adjustments chapters. Hosted on this wiki: File:Macintosh 128k.512k.pdf.
  2. ↑ 2.0 2.1 apple-history.com, Macintosh 512K (secondary source, used for the introduction price, codename and market dates).
  3. ↑ Larry Pina, The Dead Mac Scrolls, Peachpit Press, 1992, "Early Macs" chapter. Hosted on this wiki: File:The Dead Mac Scrolls 1992.pdf.


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