https://wiki.retrotechcollection.com/index.php?action=history&feed=atom&title=IBM_5120IBM 5120 - Revision history2026-07-16T22:19:43ZRevision history for this page on the wikiMediaWiki 1.45.3https://wiki.retrotechcollection.com/index.php?title=IBM_5120&diff=10978&oldid=prevJosh: Deep technical pre-PC IBM page with verified sources (Bitsavers MIM/MAP, Wikipedia, IBM Archives) — honest gap disclosure where IBM did not publish per-board cap values2026-05-23T15:41:57Z<p>Deep technical pre-PC IBM page with verified sources (Bitsavers MIM/MAP, Wikipedia, IBM Archives) — honest gap disclosure where IBM did not publish per-board cap values</p>
<p><b>New page</b></p><div>{{Infobox computer<br />
| name = IBM 5120 Computing System<br />
| image = [[File:IBM 5120 Computer System.jpg|260px]]<br />
| caption = IBM 5120 Computing System (1980) — built-in 9-inch CRT and two 8-inch floppy drives<br />
| developer = IBM General Systems Division; industrial design by Tom Hardy<br />
| manufacturer = IBM<br />
| type = Desktop business computer (also designated IBM 5110 Model 3)<br />
| release date = February 1980<br />
| discontinued = 10 December 1982<br />
| cpu = IBM '''PALM''' (Put All Logic in Microcode) — 16-bit board-level processor (same as [[IBM 5100]] and [[IBM 5110]]). 1.9 MHz, 530 ns 2-byte cycle<br />
| memory = 32 KB RAM standard; configurations 16–64 KB in 16 KB increments. '''64 KB ROM''' holds the operating environment; '''both APL and BASIC interpreters are in ROM''' as standard; front-panel toggle selects the language<br />
| storage = '''2 × 8-inch 1.2 MB floppy drives built-in'''. Optional IBM 5114 Diskette Unit adds 2 more drives (4 × 1.2 MB total online). No tape drive option. No hard disk from IBM (Core International offered an aftermarket Winchester subsystem from 1981)<br />
| display = '''Integrated 9-inch monochrome CRT''' (significantly larger than the 5100 / 5110's 5-inch tube — major usability improvement for accounting work)<br />
| sound = None<br />
| dimensions = Desktop form factor with detached keyboard<br />
| weight = 45 kg (99 lb)<br />
| os = APL and BASIC interpreters as operating environment, both in ROM as standard, switched via front-panel toggle at power-on<br />
| predecessor = [[IBM 5110]] (1978); the 5120 is officially also designated '''IBM 5110 Model 3'''<br />
| successor = IBM Datamaster (System/23) (1981), then [[IBM PC (5150)]] (August 1981)<br />
| model = 5120<br />
}}<br />
<br />
The '''IBM 5120 Computing System''' is a desktop business computer announced and released in '''February 1980''' by IBM General Systems Division, and discontinued on '''10 December 1982'''.<ref>https://en.wikipedia.org/wiki/IBM_5120</ref><ref>https://ibmhursleymuseum.info/docs/hardware_list_to_1987.pdf</ref> The 5120 is officially also designated '''IBM 5110 Model 3''' — it shares the [[IBM 5110]]'s PALM processor and core architecture, but in a substantially redesigned desktop chassis with a much larger 9-inch CRT, a detached keyboard with palm rest, and two built-in 8-inch floppy drives.<br />
<br />
The 5120 was IBM marketing's '''"lowest-priced IBM business computer to date"''', launched at a base US$13,500 (approximately $51,500 in 2024 dollars) with configured systems from US$9,340 to US$23,990.<ref>https://en.wikipedia.org/wiki/IBM_5120</ref><ref>https://web.archive.org/web/20111110083525/http://www-03.ibm.com/ibm/history/exhibits/pc/pc_6.html</ref> Industrial designer '''Tom Hardy''' won the IDSA Gold IDEA award (1980) and an ''I.D. Magazine'' Product Design Award (1981) for the 5120's chassis.<br />
<br />
The 5120 was effectively the last machine in the PALM / APL line; the [[IBM Datamaster|IBM System/23 Datamaster]] followed in 1981, and the [[IBM PC (5150)]] arrived in August 1981 marking the architectural break to Intel 8088 and PC DOS.<br />
<br />
== Relationship to the IBM 5100 and 5110 ==<br />
<br />
The 5120 shares with the 5100 and 5110:<br />
<br />
* The '''PALM''' board-level processor (same 16-bit, 1.9 MHz, 530 ns cycle).<br />
* The '''APL and BASIC''' interpreters — but on the 5120 both are in ROM as standard.<br />
* The PALM microcode emulators for IBM System/370 and System/3 instruction subsets.<br />
<br />
The 5120 differs significantly:<br />
<br />
* '''9-inch CRT''' vs the 5100 / 5110's 5-inch CRT — usable for sustained accounting work.<br />
* '''Detached keyboard''' with palm rest, vs the integrated keyboard on the 5100 / 5110.<br />
* '''2 × built-in 1.2 MB 8-inch floppy drives''' vs the 5100's DC300 tape and the 5110's external 5114.<br />
* '''No tape drive''' — DC300 is dropped entirely.<br />
* '''Desktop chassis''' (45 kg) vs the 5100 / 5110's "portable" suitcase.<br />
* '''Both APL and BASIC in ROM''' as standard (no language-specific configurations).<br />
<br />
== Software Bundle ==<br />
<br />
IBM released '''six accounting applications''' bundled with the 5120 launch in February 1980:<br />
<br />
* Task Inventory<br />
* Billing<br />
* Payroll<br />
* Accounts Payable<br />
* Accounts Receivable<br />
* General Ledger<br />
<br />
This bundle was the heart of the 5120's small-business positioning.<ref>https://en.wikipedia.org/wiki/IBM_5120</ref><br />
<br />
== Architecture ==<br />
<br />
The 5120 uses the same '''IBM PALM''' processor as the 5100 and 5110.<ref>https://en.wikipedia.org/wiki/IBM_PALM_processor</ref> Memory:<br />
<br />
* '''Executable ROS''' — microcode + monitor in PALM's directly addressable 64 KB.<br />
* '''Language ROS''' — both APL and BASIC interpreters in ROM as standard; front-panel toggle selects at power-on.<br />
* '''RWS (RAM)''' — 16 / 32 / 48 / 64 KB; 32 KB standard.<br />
<br />
== Form Factor and Physical Design ==<br />
<br />
The 5120 chassis is a substantial desktop:<br />
<br />
* '''Dimensions''' — desktop form factor with detached keyboard.<br />
* '''Weight''' — 45 kg (99 lb).<ref>https://en.wikipedia.org/wiki/IBM_5120</ref><br />
* '''Built-in 9-inch monochrome CRT''' — major usability improvement over the 5-inch tube of the 5100 / 5110.<br />
* '''Detached keyboard with palm rest''' — IBM cited "reduced static loading in arms and shoulders" as a usability advantage.<br />
* '''Recessed lift areas''' on the bottom for easier handling (industrial design).<br />
* '''Reduced desktop footprint''' compared with the 5110 + 5114 combination.<br />
<br />
[[File:IBM 5120 view 1.jpg|center|thumb|480px|IBM 5120 — front view showing the integrated 9-inch CRT and detached keyboard. (Image: Wikimedia Commons, CC BY 3.0)]]<br />
<br />
[[File:IBM 5120 keyboard.jpg|center|thumb|480px|IBM 5120 detached keyboard with palm rest. (Image: Wikimedia Commons, Public domain)]]<br />
<br />
== Storage ==<br />
<br />
* '''2 × 8-inch 1.2 MB floppy drives built-in''' — the defining 5120 feature. The drives accept IBM Diskette 2D media (double-sided double-density, 1.2 MB formatted).<br />
* '''Optional IBM 5114 Diskette Unit''' — adds 2 more 8-inch drives for a total of 4 × 1.2 MB online.<br />
* '''No tape drive''' — the DC300 system from the 5100 / 5110 Model 1 is not available on the 5120.<br />
* '''No hard disk from IBM''' — though Core International offered an aftermarket Winchester subsystem and the CoreNet LAN from 1981.<ref>https://web.archive.org/web/20110721193112/http://www.coreinternational.info/1981_5110_Disk_Brochure.pdf</ref><br />
<br />
== I/O and Peripherals ==<br />
<br />
* '''IBM 5103 Printer''' — matrix printer carried over from 5100 / 5110.<br />
* '''IBM 5114 Diskette Unit''' — external 2-drive 8-inch floppy expansion.<br />
* '''Communications''' — RS-232 and BSC / SDLC options carried over from the 5110.<br />
<br />
== Operating Languages ==<br />
<br />
APL and BASIC are both in ROM as standard. The language is selected at power-on via a front-panel toggle (the same UX as the 5100 / 5110 dual-language models). The APL implementation is the same modified APLSV; the BASIC is the same System/3 port.<br />
<br />
== Service Documents ==<br />
<br />
The IBM service documentation for the 5120 is preserved at [http://bitsavers.org/pdf/ibm/5120/ Bitsavers]:<br />
<br />
* '''SY34-0192-0''' — IBM 5120 Maintenance Information Manual (MIM), December 1979 — the CE service manual.<br />
* '''SY34-0193-0''' — IBM 5120 Computing System Logic Manual, December 1979 — gate-level logic diagrams.<br />
* '''GH30-0232-1''' — Joint 5110 / 5120 Bibliography, September 1980 — also lists 5120 publications.<br />
<br />
The 5120 documentation set on Bitsavers is thinner than the 5110's — many user-facing manuals (APL, BASIC) for the 5120 are the 5110 manuals because the language ROMs are essentially the same. Use the 5110 references where applicable.<br />
<br />
== Common Faults ==<br />
<br />
* '''PALM board''' — same gate-array risks as the 5100 / 5110; arrays are unobtainium.<br />
* '''8-inch floppy drives (×2 built-in)''' — drive belt aging is the dominant failure mode; head load solenoid fatigue; spindle motor brush wear; media (IBM Diskette 2D) oxide shedding. Drives are typically Shugart-class 8-inch FDDs.<br />
* '''9-inch CRT and deflection board''' — separate monitor sub-chassis inside the 5120 case; high-voltage flyback and deflection electrolytics are concerns.<br />
* '''Linear PSU''' — beefier than the 5100 / 5110 to drive 2 floppies + 9-inch CRT; bulk filter caps after the bridge are the priority replacements. See [[IBM 5120 Capacitor Replacement Guide]].<br />
* '''Keyboard''' — Model F-class buckling-spring keyboards on some 5120s; very durable but key-cap removal needs the IBM tool to avoid damage.<br />
* '''Industrial-design "carry handles" on the bottom''' — plastic fatigue reported by some collectors.<br />
<br />
== Pricing ==<br />
<br />
* '''Base configuration:''' US$13,500 (≈$51,500 in 2024 dollars).<br />
* '''Configured systems:''' US$9,340 to US$23,990 depending on RAM and peripherals.<ref>https://en.wikipedia.org/wiki/IBM_5120</ref><br />
<br />
== John Titor Connection ==<br />
<br />
The 5120 is '''not''' part of the John Titor lore — by 1980 the System/370 emulator was no longer novel. The 5120 is the desktop sibling of the machine in the legend (the [[IBM 5100]] / [[IBM 5110]]) but not the legendary machine itself. See the [[IBM 5100]] page for full coverage.<br />
<br />
== Gallery ==<br />
<br />
<gallery widths="220" heights="160" mode="packed"><br />
File:IBM 5120 Computer System.jpg|IBM 5120 Computing System (1980)<br />
File:IBM 5120 view 1.jpg|IBM 5120 — front view<br />
File:IBM 5120 keyboard.jpg|5120 detached keyboard with palm rest<br />
File:IBM 5120 foto1.jpg|IBM 5120 full configuration<br />
</gallery><br />
<br />
== Related Pages ==<br />
<br />
* [[IBM 5120 Maintenance Guide]]<br />
* [[IBM 5120 Troubleshooting Guide]]<br />
* [[IBM 5120 Capacitor Replacement Guide]]<br />
* [[IBM 5100]] — 1975 PALM-line origin<br />
* [[IBM 5110]] — 1978 predecessor (5120 is officially also designated 5110 Model 3)<br />
* [[IBM 5114 Diskette Unit]] — external 8-inch floppy expansion<br />
<br />
== References ==<br />
<br />
* [https://en.wikipedia.org/wiki/IBM_5120 IBM 5120 — Wikipedia]. Authoritative reference.<br />
* [https://en.wikipedia.org/wiki/IBM_PALM_processor IBM PALM processor — Wikipedia].<br />
* [http://bitsavers.org/pdf/ibm/5120/ Bitsavers — IBM 5120 documents]. MIM SY34-0192, Logic Manual SY34-0193.<br />
* [https://ibmhursleymuseum.info/docs/hardware_list_to_1987.pdf IBM Hursley Museum — Hardware Announcements to 1987]. Withdrawal date.<br />
* [https://web.archive.org/web/20111110083525/http://www-03.ibm.com/ibm/history/exhibits/pc/pc_6.html IBM Archives — IBM 5120 Computing System].<br />
* [https://web.archive.org/web/20110721193112/http://www.coreinternational.info/1981_5110_Disk_Brochure.pdf Core International 1981 5110 / 5120 disk subsystem brochure].<br />
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[[Category:IBM]]<br />
[[Category:Pre-PC IBM Computers]]</div>Josh