https://wiki.retrotechcollection.com/index.php?action=history&feed=atom&title=IBM_3270_PC%2FGIBM 3270 PC/G - Revision history2026-07-17T00:44:57ZRevision history for this page on the wikiMediaWiki 1.45.3https://wiki.retrotechcollection.com/index.php?title=IBM_3270_PC/G&diff=11076&oldid=prevJosh: Deep technical XT/370 + 3270 PC family page with verified sources (IBM SA38-0037-00 Service Info Manual, IBM GA33-3141-0, IBM 1502336, Kozuh/Livingston/Spillman IBM Systems Journal 1984, seasip.info, Wikipedia)2026-05-23T21:32:15Z<p>Deep technical XT/370 + 3270 PC family page with verified sources (IBM SA38-0037-00 Service Info Manual, IBM GA33-3141-0, IBM 1502336, Kozuh/Livingston/Spillman IBM Systems Journal 1984, seasip.info, Wikipedia)</p>
<p><b>New page</b></p><div>{{Infobox computer<br />
| name = IBM 3270 PC/G<br />
| image = [[File:IBM AT GX Computer cropped.jpg|260px]]<br />
| caption = IBM 3270 PC/G — XT-derived graphics-terminal workstation (machine type 5371) announced July 1984 (representative image of related 3270 PC family unit)<br />
| developer = IBM Entry Systems Division, Boca Raton, in cooperation with IBM 3270 / GDDM groups<br />
| manufacturer = IBM<br />
| type = Mainframe graphics-terminal-emulation workstation<br />
| release date = July 1984<br />
| discontinued = 1987 (alongside the rest of the 3270 PC line)<br />
| cpu = Intel 8088 @ 4.77 MHz — same chassis as [[IBM 3270 PC]]<br />
| memory = 384 / 512 / 576 KB depending on submodel<br />
| storage = 5.25" 360 KB DSDD floppy (1 or 2) + optional hard disk<br />
| display = '''IBM 5278 Display Attachment Unit''' (external converter box) driving '''IBM 5279 Color Display''' (14"). Resolution: '''720 × 512 APA''' (colour) plus CGA-compatible 320 × 200 / 640 × 200 modes<br />
| sound = PC speaker<br />
| os = '''3270 PC Graphics Control Program (GCP)''' + PC DOS — a mainframe-graphics-aware variant of the [[IBM 3270 PC|3270 PC Control Program]], with local pan / zoom support for GDDM-generated images<br />
| predecessor = [[IBM 3270 PC]] (5271 — text-only mainframe-terminal version)<br />
| successor = IBM 3270 Workstation Program with graphics-capable adapter (1987+); IBM 6090 Graphics System for high-end CAD/CAM workloads<br />
| model = '''5371''' — same system unit machine type as the [[IBM 3270 PC/GX]] (not 5372). The /G is differentiated from the /GX by its 5278 / 5279 display pair (vs the /GX's 5378 / 5379)<br />
}}<br />
<br />
The '''IBM 3270 PC/G''' is the graphics-terminal-emulation variant of the [[IBM 3270 PC]] family, announced by IBM in '''July 1984'''. The "G" suffix designates '''Graphics''' — the /G provides high-resolution vector graphics support for IBM's '''GDDM''' (Graphical Data Display Manager) release 4+ mainframe graphics applications, with '''local pan and zoom''' that does not require a round-trip to the host mainframe.<ref>IBM GA33-3141-0, ''Introducing the IBM 3270 Personal Computer/G and /GX Workstations'', May 1984.</ref><ref>https://en.wikipedia.org/wiki/IBM_3270_PC</ref><br />
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== Important Machine-Type Note ==<br />
<br />
The 3270 PC/G uses '''system unit 5371'''. This is '''the same machine type as the [[IBM 3270 PC/GX]]''' — there is no "5372" 3270 PC product. The /G and /GX differ by their attached display hardware:<br />
<br />
* '''3270 PC/G''' (this page): IBM '''5278''' Display Attachment Unit + IBM '''5279''' 14" Color Display, '''720 × 512''' APA.<br />
* '''[[IBM 3270 PC/GX]]''': IBM '''5378''' Display Attachment Unit + IBM '''5379''' 19" Color Display, '''1024 × 1024''' APA.<br />
<br />
The AT-based equivalent (PC AT/G and AT/GX) uses '''system unit 5373''', not 5371.<br />
<br />
The 5371 system unit is '''a different machine type from the 5271''' base 3270 PC, and '''a basic 5271 cannot be upgraded to a /G or /GX'''.<br />
<br />
== Launch and Pricing ==<br />
<br />
* Announced July 1984 alongside the /GX.<br />
* Reference document: IBM '''GA33-3141-0''' ''Introducing the IBM 3270 Personal Computer/G and /GX Workstations'' (May 1984).<br />
* Launch price: '''$11,240''' retail for a working PC/G configuration with display.<ref>https://en.wikipedia.org/wiki/IBM_3270_PC</ref><br />
* Model 16 (system unit alone, without graphics) was $6,580.<br />
* '''Discontinued 1987''' alongside the rest of the 3270 PC line, after IBM released the 3270 Workstation Program software for standard PCs and PS/2s.<br />
<br />
== Models ==<br />
<br />
{| class="wikitable styled-table" style="width:100%; text-align:center;"<br />
|+'''IBM 3270 PC/G (5371) submodels'''<br />
! Submodel !! Storage !! RAM<br />
|-<br />
| 12 || 1 × floppy || 384 KB<br />
|-<br />
| 14 || 2 × floppy || 512 KB<br />
|-<br />
| 16 || floppy + HDD || 576 KB<br />
|}<br />
<br />
'''Model 12 has a parallel port and the IBM 5277 mouse as standard''' — the higher-end models add the mouse as well but were originally shipped without it.<br />
<br />
== Hardware ==<br />
<br />
The 5371 system unit is a different machine type from the 5271 (3270 PC) but uses the same overall card-set approach. Specific to the PC/G:<br />
<br />
* '''IBM 5278 Display Attachment Unit''' — separate external box "packed with circuitry" — drives the 5279 monitor via a '''75-pin connector'''. The 5278 carries the active vector-graphics hardware.<br />
* '''IBM 5279 Color Display''' — 14" colour CRT paired with the 5278 attachment box.<br />
* '''IBM 5277 mouse''' — 3-button, $340 standalone.<br />
* All other cards (Keyboard Adapter, 3270 PC Display Adapter, APA, PSS, 3278/79 Emulation Adapter) are the same as the standard [[IBM 3270 PC]].<br />
<br />
== Resolution and Graphics ==<br />
<br />
* '''720 × 512 APA''' in colour — the defining 3270 PC/G capability.<br />
* CGA-compatible '''320 × 200 / 640 × 200''' modes for DOS software.<br />
* Full-screen colour-mapped graphics suitable for mainframe-generated GDDM plots, CAD-style line drawings, and business charts.<br />
<br />
== Operating Environment: Graphics Control Program (GCP) ==<br />
<br />
The 3270 PC/G runs the '''Graphics Control Program (GCP)''' — a mainframe-graphics-aware variant of the standard 3270 PC Control Program. GCP adds:<br />
<br />
* Support for '''GDDM release 4+''' mainframe graphics protocols.<br />
* '''Local pan / zoom''' of graphics images — manipulation happens in the 5278's local memory without round-tripping every operation back to the mainframe.<br />
* '''Mouse support''' via the IBM 5277.<br />
* Multi-session windowing (up to 4 mainframe sessions + 1 DOS task + 2 notepads), the same as the standard 3270 PC.<br />
<br />
GDDM release 4 (and later releases) on the mainframe must be configured to talk to the /G workstation.<ref>https://www.ibm.com/docs/en/gddm?topic=gddm-3270-pcg-3270-pcgx-workstations</ref><br />
<br />
== Relationship to the IBM 3179G Terminal ==<br />
<br />
The 3270 PC/G is sometimes informally described as a workstation equivalent of the dedicated '''IBM 3179G Color Graphics Display Station'''. In fact the two products are '''contemporary''' — the 3179G was announced on '''18 June 1985''', '''after''' the PC/G's July 1984 launch. The PC/G is therefore '''not''' a "replacement" for the 3179G; rather, they are sibling products serving similar use cases via different chassis (PC/G = workstation with local DOS; 3179G = dedicated terminal with no local computing).<br />
<br />
== Common Faults ==<br />
<br />
The PC/G inherits all of the chassis-level faults of the [[IBM 3270 PC]] (RIFA mains-suppression caps in the PSU; tantalum bypass shorts on the planar; ageing 130 W IBM XT PSU). PC/G-specific faults:<br />
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* '''IBM 5278 Display Attachment Unit''' — separate enclosure with its own PSU and active vector-graphics circuitry. This is '''the rarest single component in the PC/G system''' after 40+ years and is the most likely failure point. The 5278 is not interchangeable between PC/G and PC/GX configurations (the /GX uses the larger 5378).<br />
* '''IBM 5279 14" colour CRT''' — dedicated tube and timings; failure means substituting an IBM 5151 monochrome display (losing all graphics modes) is the only practical recovery.<br />
* '''75-pin cable''' between 5278 and 5279 — proprietary; can develop intermittent contact at the connectors.<br />
* '''GCP system diskettes''' are rare in 2024; image them immediately if you have a working installation.<br />
<br />
== Service Documents ==<br />
<br />
* '''IBM GA33-3141-0''' — ''Introducing the IBM 3270 Personal Computer/G and /GX Workstations'' (May 1984). Primary reference document.<ref>https://www.bitsavers.org/pdf/ibm/pc/3270/3270_PC/GA33-3141-0_Introducing_the_IBM_3270_Personal_Computer_G_and_GX_Workstations_198405.pdf</ref><br />
* '''IBM SA38-0037-00''' — ''Personal Computer Family Service Information Manual'' (July 1989), Chapter 10.<br />
<br />
== Related Pages ==<br />
<br />
* [[IBM 3270 PC/G Maintenance Guide]]<br />
* [[IBM 3270 PC/G Troubleshooting Guide]]<br />
* [[IBM 3270 PC/G Capacitor Replacement Guide]]<br />
* [[IBM 3270 PC]] — base 5271 text-only family member<br />
* [[IBM 3270 PC/GX]] — extended-graphics sibling (also system unit 5371)<br />
* [[IBM PC XT (5160)]] — chassis ancestor<br />
<br />
== References ==<br />
<br />
* [https://www.bitsavers.org/pdf/ibm/pc/3270/3270_PC/GA33-3141-0_Introducing_the_IBM_3270_Personal_Computer_G_and_GX_Workstations_198405.pdf IBM GA33-3141-0 (May 1984)]. Primary PC/G and /GX reference.<br />
* [https://en.wikipedia.org/wiki/IBM_3270_PC IBM 3270 PC — Wikipedia].<br />
* [https://www.ibm.com/docs/en/gddm?topic=gddm-3270-pcg-3270-pcgx-workstations IBM GDDM Documentation — 3270 PC/G and 3270 PC/GX Workstations].<br />
* [http://bitsavers.org/pdf/ibm/pc/SA38-0037-00_Personal_Computer_Family_Service_Information_Manual_Jul89.pdf IBM SA38-0037-00 (July 1989)], Chapter 10.<br />
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