Editing IBM 3270 PC/G

{{Infobox computer
| name          = IBM 3270 PC/G
| image         = [[File:IBM AT GX Computer cropped.jpg|260px]]
| caption       = IBM 3270 PC/G — XT-derived graphics-terminal workstation (machine type 5371) announced July 1984 (representative image of related 3270 PC family unit)
| developer     = IBM Entry Systems Division, Boca Raton, in cooperation with IBM 3270 / GDDM groups
| manufacturer  = IBM
| type          = Mainframe graphics-terminal-emulation workstation
| release date  = July 1984
| discontinued  = 1987 (alongside the rest of the 3270 PC line)
| cpu           = Intel 8088 @ 4.77 MHz — same chassis as [[IBM 3270 PC]]
| memory        = 384 / 512 / 576 KB depending on submodel
| storage       = 5.25" 360 KB DSDD floppy (1 or 2) + optional hard disk
| 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
| sound         = PC speaker
| 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
| predecessor   = [[IBM 3270 PC]] (5271 — text-only mainframe-terminal version)
| successor   = IBM 3270 Workstation Program with graphics-capable adapter (1987+); IBM 6090 Graphics System for high-end CAD/CAM workloads
| 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)
}}

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>

== Important Machine-Type Note ==

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:

* '''3270 PC/G''' (this page): IBM '''5278''' Display Attachment Unit + IBM '''5279''' 14" Color Display, '''720 × 512''' APA.
* '''[[IBM 3270 PC/GX]]''': IBM '''5378''' Display Attachment Unit + IBM '''5379''' 19" Color Display, '''1024 × 1024''' APA.

The AT-based equivalent (PC AT/G and AT/GX) uses '''system unit 5373''', not 5371.

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'''.

== Launch and Pricing ==

* Announced July 1984 alongside the /GX.
* Reference document: IBM '''GA33-3141-0''' ''Introducing the IBM 3270 Personal Computer/G and /GX Workstations'' (May 1984).
* Launch price: '''$11,240''' retail for a working PC/G configuration with display.<ref>https://en.wikipedia.org/wiki/IBM_3270_PC</ref>
* Model 16 (system unit alone, without graphics) was $6,580.
* '''Discontinued 1987''' alongside the rest of the 3270 PC line, after IBM released the 3270 Workstation Program software for standard PCs and PS/2s.

== Models ==

{| class="wikitable styled-table" style="width:100%; text-align:center;"
|+'''IBM 3270 PC/G (5371) submodels'''
! Submodel !! Storage !! RAM
|-
| 12 || 1 × floppy || 384 KB
|-
| 14 || 2 × floppy || 512 KB
|-
| 16 || floppy + HDD || 576 KB
|}

'''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.

== Hardware ==

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:

* '''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.
* '''IBM 5279 Color Display''' — 14" colour CRT paired with the 5278 attachment box.
* '''IBM 5277 mouse''' — 3-button, $340 standalone.
* All other cards (Keyboard Adapter, 3270 PC Display Adapter, APA, PSS, 3278/79 Emulation Adapter) are the same as the standard [[IBM 3270 PC]].

== Resolution and Graphics ==

* '''720 × 512 APA''' in colour — the defining 3270 PC/G capability.
* CGA-compatible '''320 × 200 / 640 × 200''' modes for DOS software.
* Full-screen colour-mapped graphics suitable for mainframe-generated GDDM plots, CAD-style line drawings, and business charts.

== Operating Environment: Graphics Control Program (GCP) ==

The 3270 PC/G runs the '''Graphics Control Program (GCP)''' — a mainframe-graphics-aware variant of the standard 3270 PC Control Program. GCP adds:

* Support for '''GDDM release 4+''' mainframe graphics protocols.
* '''Local pan / zoom''' of graphics images — manipulation happens in the 5278's local memory without round-tripping every operation back to the mainframe.
* '''Mouse support''' via the IBM 5277.
* Multi-session windowing (up to 4 mainframe sessions + 1 DOS task + 2 notepads), the same as the standard 3270 PC.

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>

== Relationship to the IBM 3179G Terminal ==

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).

== Common Faults ==

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:

* '''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).
* '''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.
* '''75-pin cable''' between 5278 and 5279 — proprietary; can develop intermittent contact at the connectors.
* '''GCP system diskettes''' are rare in 2024; image them immediately if you have a working installation.

== Service Documents ==

* '''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>
* '''IBM SA38-0037-00''' — ''Personal Computer Family Service Information Manual'' (July 1989), Chapter 10.

== Related Pages ==

* [[IBM 3270 PC/G Maintenance Guide]]
* [[IBM 3270 PC/G Troubleshooting Guide]]
* [[IBM 3270 PC/G Capacitor Replacement Guide]]
* [[IBM 3270 PC]] — base 5271 text-only family member
* [[IBM 3270 PC/GX]] — extended-graphics sibling (also system unit 5371)
* [[IBM PC XT (5160)]] — chassis ancestor

== References ==

* [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.
* [https://en.wikipedia.org/wiki/IBM_3270_PC IBM 3270 PC — Wikipedia].
* [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].
* [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.

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