IBM 3270 PC: Difference between revisions

| memory        = 256 KB on the system board on Models 002, 004, 006, 024, 026, 031, 051 and 071; '''640 KB''' on the system board on Models 030, 050 and 070. Models 004, 006, 024, 026 and 051 add a Printer/Memory Adapter carrying a further 128 KB; Models 031, 051 and 071 carry an '''Expanded Memory Adapter (XMA) with 1 MB'''

| storage      = 5.25-inch 360 KB diskette drive (full-height on Models 002–026, half-high on Models 030 onwards), one or two. '''10 MB''' fixed disk on Models 006 and 026; '''20 MB''' on Models 070 and 071 only — Models 030 and 050 are diskette-only

| model        = 5271 (system unit machine type). Submodels 002, 004, 006, 024, 026, 030, 031, 050, 051, 070, 071, and the P variants P30, P31, P50, P51, P70 and P71, which swap the 5271 keyboard for the 101-key Enhanced Keyboard and a Cable Adapter and require Control Program 3.0

The '''IBM 3270 PC''' (machine type '''5271''') is a mainframe-terminal-emulation workstation announced by IBM on '''18 October 1983''' (announcement letter '''183-129''').<ref name="al183129">IBM Announcement Letter 183-129, 18 October 1983, mirrored at <code>sharktastica.co.uk/resources/docs/IBM_183-129_3270PC_83.pdf</code>.</ref> The system unit is an [[IBM PC XT (5160)]] with the expansion slots almost entirely occupied by specialist 3270 cards. IBM says so itself, in the parts catalogue: '''"all base system parts for the 3270 XT products are the same as 5160 XT base system parts"'''.<ref name="sim">IBM, ''IBM Personal Computer Family Service Information Manual'', SA38-0037-00, July 1989 &mdash; hosted on this wiki as [[IBM Personal Computer Family Service Information Manual]]. Chapter 10, "3270 PC Products", is the source for the system-unit and display combinations, the full 5271, 5371 and 5373 model lists, the 5371 and 5373 slot allocations, the unit specifications for the 5371, 5278, 5279, 5378 and 5379, the statement of which unit powers which, the 3270 unique error code to FRU indication table, the diagnostic tips and the ECA history. Chapter 18, "Personal Computer Parts Catalog", is the source for the 5271, 5371 and 5373 FRU part numbers and for IBM's note that "all base system parts for the 3270 XT products are the same as 5160 XT base system parts".</ref> That is the single most useful fact about servicing one &mdash; planar, power supply, drives, covers and keyboard cable are all XT parts, and only the 3270 cards and the displays are unique. The combination of these cards plus the '''3270 PC Control Program''' allows the workstation to host '''up to four mainframe terminal sessions, one DOS task, and two notepads''' simultaneously in a windowed display — a unique capability in 1983.<ref name="wp3270">Wikipedia, "IBM 3270 PC". Tertiary; used for the launch and withdrawal chronology and the retail prices.</ref>

 

{| class="wikitable styled-table" style="width:100%;"

|+'''IBM 3270 PC (5271) models'''

! Model !! System board RAM !! Display adapter !! Diskette !! Fixed disk !! Other

| '''030''' || '''640 KB''' || 5151/5272 || 1 × 360 KB half-high || &mdash; || Printer Adapter

| '''050''' || '''640 KB''' || 5151/5272 || 2 × 360 KB half-high || &mdash; ||

| '''070''' || '''640 KB''' || 5151/5272 || 1 × 360 KB half-high || '''20 MB''' ||

| '''031''' || 256 KB || 5151/5272 || 1 × 360 KB half-high || &mdash; || '''XMA with 1 MB''' (includes Printer Adapter); needs Control Program 3.0

| '''051''' || 256 KB || 5151/5272 || 2 × 360 KB half-high || &mdash; || XMA with 1 MB; Printer/Memory Adapter with 128 KB; Control Program 3.0

| '''071''' || 256 KB || 5151/5272 || 1 × 360 KB half-high || '''20 MB''' || XMA with 1 MB; Control Program 3.0

| '''P30, P31, P50, P51, P70, P71''' || colspan="5" | As the corresponding numeric model, except that an '''Enhanced (101-key) Keyboard and a Cable Adapter''' replace the 5271 Keyboard. All P models require Control Program 3.0.

Three things in that table are commonly got wrong:

* '''Only Models 070 and 071 have the 20 MB fixed disk.''' Models 030 and 050 are diskette-only despite being in the same 1986 group.

* '''The XMA carries 1 MB, not 2 MB.'''

* '''Models 024 and 026 use a different keyboard adapter''' &mdash; IBM calls it the '''Plasma Keyboard Adapter''' &mdash; alongside the 3295 Plasma Display Adapter. A standard Keyboard Adapter is not a substitute.

 

IBM also records a documented trap for the XMA: '''jumpered as LPT2 on a 5271 with a fixed disk, the XMA is not supported''' &mdash; there is an interrupt-level conflict.<ref name="sim" />

* '''Model 006''' (256 KB system board plus a 128 KB Printer/Memory Adapter, with the 10 MB fixed disk): '''$6,210''' for the system unit alone.<ref name="wp3270" />

* Typical working colour-monitor configuration: about '''$8,465''' including software and cabling.<ref name="pcmag85">''PC Magazine'', 22 January 1985, Valenzuela review of the 3270 PC. Also the source of the "memory hog" characterisation of the Control Program.</ref>

* '''Critical: this card holds the video BIOS''' for the 3270 PC Display Adapter — the video cards do not work without the keyboard adapter card installed.<ref name="seasip">John Elliott, [http://www.seasip.info/VintagePC/5271.html The IBM 5271 (aka 3270 PC)], seasip.info. A community technical reference built from a working machine: the card complement and what each card does, the video BIOS living in the keyboard controller ROM (part 6323581 for the "simple" controller and 6323582 for the "complicated" one), the error codes 3201, 3202, 3203 and 2801, the 5272 display timings, and the statement that the case, motherboard, drives and power supply are all identical or very similar to the XT.</ref>

* On Models 024 and 026, which drive the 3295 Plasma Monitor, IBM fits a '''Plasma Keyboard Adapter''' in place of the standard one.<ref name="sim" />

* '''Coaxial''' connection to an IBM '''3274''' (later 3174) control unit. '''It is coax, not twinax''' — twinax is the midrange 5250 attachment and will not work here — and the link is point to point, one control-unit port per workstation, with '''no terminator'''.<ref name="mi3270" /><ref name="sim" />

* Technical reference: '''IBM 1502336''' — ''PC 3278/79 Emulation Adapter Technical Reference'' (October 1983), at <code>bitsavers.org/pdf/ibm/pc/cards/</code>.

In '''1987''' the '''3270 Workstation Program''' (IBM '''84X0982''') replaced the Control Program, providing the same multi-session experience on a standard XT or AT with only a 3278/79 Emulation Adapter — and adding DOS 3.3 support plus up to six DOS sessions.<ref name="wsp87">IBM, ''3270 Workstation Program Version 1.0 User's Guide and Reference'', 84X0982, April 1987, at <code>bitsavers.org/pdf/ibm/pc/3270/</code>.</ref>

* '''IBM 5272 Color Display''' — 14" tilt/swivel, '''720 × 350''' in '''7 colours''' (no high-intensity; bright and standard CGA colours render identically). Pin 4 of the DE-9 selects mono vs colour. Color timings: '''hsync 24 kHz negative, vsync 63 Hz negative'''. Mono timings: 18.6 kHz / 50 Hz.<ref name="seasip" />

* First announced October 1983; shipped Q1 1984.<ref name="kbwiki">[https://sharktastica.co.uk/wiki/ibm-model-f sharktastica.co.uk &mdash; IBM Model F] and [https://deskthority.net/wiki/IBM_Model_F_122-key deskthority &mdash; IBM Model F 122-key]. Community keyboard references; the source for the 9.3 lb weight and the scan-code-set-3 behaviour. </ref> IBM's own parts catalogue lists keyboard part '''6110344''' for the 5271 in Figure 7 of the maintenance manual.<ref name="mi3270" />

The chassis is a stock IBM PC XT — IBM says so in its own parts catalogue<ref name="sim" /> — so chassis faults are XT faults:

* '''Tantalum bypass capacitor shorts''' on the planar — these pull the +5 V rail down. The 5160 board carries sixteen tantalums, thirteen of them on +5 V, and they fail at or shortly after power-on.<ref name="mz">[https://www.minuszerodegrees.net/failure/failure.htm Commonly Failing Electronic Components (in vintage computers)] and [https://www.minuszerodegrees.net/5150_5160/MDC/tantalum_short_plus_5volts.htm Short-circuit on the +5 volt line of an IBM 5150/5155/5160 motherboard], minuszerodegrees.net. Sources for the tantalum failure modes on 51xx boards and for the count of sixteen tantalums on the 5160 motherboard, thirteen of them on the +5 V line. Community sources that mirror IBM data; they apply to the 3270 PC because IBM states the base system parts are the same as the 5160 XT's.</ref>

* '''Keyboard adapter dongle cable''' — wear, missing, or pin damage. The pinout is documented at seasip.info and is reproducible.<ref name="seasip" />

* '''Capacitor failure''' — seasip.info documents a 5271 planar that "failed with a blown capacitor".<ref name="seasip" />

<references />

 

 

* [[IBM 3270 PC Maintenance Information]] and [[IBM Personal Computer Family Service Information Manual]] — both hosted here, and the two documents this page is built on.