IBM System/360 Model 50: Difference between revisions

Revision as of 21:29, 29 October 2021

Latest revision as of 01:09, 6 July 2025

(13 intermediate revisions by 9 users not shown)

Line 1:

{{Short description|Midrange IBM computer from 1960s}}

{{Infobox information appliance

| name = IBM System/360 Model 50

Line 16 ⟶ 17:

| lifespan =

| price =

| discontinued = {{End date|1977|03|15}}<ref>{{cite web|last1=IBM Corporation|title=IBM Archives: System/360 Model 50|url=https://www-03.ibm.com/ibm/history/exhibits/mainframe/mainframe_PP2050.html|website=IBM Archives|accessdatedate=June23 29,January 20172003|archive-url=https://web.archive.org/web/20230928074645/https://www.ibm.com/ibm/history/exhibits/mainframe/mainframe_PP2050.html|archive-date=2023-09-28|url-status=dead}}</ref>

| unitssold =

| unitsshipped =

Line 52 ⟶ 53:

===Relative performance===

The system has a CPU cycle time of 500 nanoseconds, 25% faster than the [[IBM System/360 Model 40|Model 40]] and 40% slowerof thanthe speed of the [[IBM System/360 Model 65|Model 65]] which has a 200 nanosecond cycle time. Processor storage is [[magnetic core memory]] that transfers four bytes per 2 microsecond cycle. It has "protected" and "local" core storage for registers and internal buffers with cycle times of 200 and 500 nanoseconds respectively.

==Features==

Line 60 ⟶ 61:

==Microcode==

The Model 50 uses a 90&nbsp;bit (or 85&nbsp;bit, depending on definition) "horizontal microcode" instruction format, with each word containing 15 (or 25) separate fields.<ref>{{cite web|last1=Smotherman|first1=Mark|title=A Brief History of Microprogramming|url=http://ed-thelen.org/comp-hist/MicroprogrammingABriefHistoryOf.pdf|accessdate=Sep 26, 2015}}</ref> There are 2816 words of microcode storage.<ref>{{cite book|editor-last1=Kent|editor-first1=Allen (ed)|editor-last2=Williams|editor-first2=James G. (ed)|title=Encyclopedia of Computer Science and Technology volume 28|date=1993|publisher=CRC Press|isbn=978-0-8247-2281-4|page=39|url=https://books.google.com/books?id=EjWV8J8CQEYC|accessdate=Sep 26, 2015}}</ref>

Read-only control storage for microcode employs "balanced capacitor technology" (BCROS) with a cycle time of 500 nanoseconds, designed by Anthony Proudman in [[IBM Hursley|IBM's Hursley laboratory]] and implemented by Fernando "Fred" Neves. This technology uses two [[capacitor]]s to represent each bit.

[[File:IBM1970 360-50,CNRZ ZETOMécanographie-8-cliche ZOWARJean (I197703)Weber.jpg|thumb|right|B&W closeup of 360/50 console]]

==System software==

It was possible to choose [[DOS/360]], [[OS/360 and successors#MFT|OS/360 MFT]] (Multi-programming with a Fixed number of Tasks), or [[OS/360 and successors#MVT|OS/360 MVT]] (Multi-programming with a Variable number of Tasks) as the [[Operatingoperating Systemsystem]] of an IBM System/360 Model 50. Few chose MVT.<ref name="most-didnt-run-mvt">{{cite mailing list|url=https://groups.google.com/forum/#!original/bit.listserv.ibm-main/zqAApnIeXec/qZ-fhTcVKz0J|title=Re:the 40thconsole anniversarysubsystem ofpriority IBM|via=Google System/360Groups on 7 Apr 2004|date=January 18, 2004|author=William H. Blair|mailing-list=ibm-main|quote=Your point is well taken. But most didn't run MVT, and many that did had LCS (Large Capacity Storage). MVT was not very popular. Nonetheless, I ran a system that ran MVT just fine with only 256MB; maximum REGION size was 114MB, which was perfectly fine for the workload. I suspect that if MVT was being used on a /65 or /75, then 512KB was installed. But, there were a lot of folks that ran MVT on a /50 with 384KB. We got blood out of the turnip back in those days. |url-status=live |archive-url=https://archive.today/20240410212204/https://groups.google.com/g/bit.listserv.ibm-main/c/zqAApnIeXec/m/qZ-fhTcVKz0J |archive-date= 10 April 2024 }}</ref>

The choice of operating system for the System/360 Model 50 was based primarily on the amount of main storage. The F50, with 65,536 bytes of main storage, can not run OS/MFT, which requires a minimum of 131,072 bytes of main storage.<ref>{{cite book|url=http://bitsavers.org/pdf/ibm/360/os/R21.7_Apr73/GC27-6939-10_MFT_Guide_R21.7_Mar72.pdf|title=IBM System/360 Operating System: MFT Guide OS Release 21.7|id=GC27-6939-10|publisher=IBM|date=March 1972|page=69 |via=bitsavers |url-status=live |archive-url= https://web.archive.org/web/20231224064716/http://bitsavers.org/pdf/ibm/360/os/R21.7_Apr73/GC27-6939-10_MFT_Guide_R21.7_Mar72.pdf |archive-date= Dec 24, 2023 }}</ref>

DOS/360 has a minimum of 16,384 bytes of main storage.<ref>{{cite book|url=http://bitsavers.org/pdf/ibm/360/dos/GC24-5030-8_Disk_and_Tape_Operating_Systems_Concepts_and_Facilities_Oct70.pdf|title=IBM System/360 Disk and Tape Operating Systems Concepts and Facilities|id=GC24-5030-8|publisher=IBM|date=October 1970|page=5}} "|via=bitsavers |quote=Disk and Tape Operating Systems are comprehensive sets of language translators and service programs operating under the supervisory coordination of an integrated control program. They require an IBM System/360 with at least 16K bytes of main storage." |url-status=live |archive-url=https://web.archive.org/web/20231224064716/http://bitsavers.org/pdf/ibm/360/dos/GC24-5030-8_Disk_and_Tape_Operating_Systems_Concepts_and_Facilities_Oct70.pdf |archive-date= Dec 24, 2023 }}</ref>

Systems with 131,072 or more bytes of main storage could run OS/360. Although 360/50 systems equipped with 1 MB or more<ref>{{cite conference|url=https://books.google.com/books?id=_BGDRGWzVw4C&pg=PA33|title=Using SMF and TFLOW for Performance Enhancement|conference=Eighth Meeting of Computer Performance Evaluation Users Group (CPEUG)|author=J. M. Graves|year=1974}}</ref> could and did run MVT<ref>{{cite mailing list|url=http://www.classiccmp.org/pipermail/cctalk/2015-May/006672.html|title=Re: 360/50 microcode listing|mailing-list=[e-mail]|date=May 7, 2015}}</ref><ref>{{cite web|url=https://www3.epa.gov/storet/pptfiles/manning.ppt|archive-url=https://web.archive.org/web/20040711025501/http://www.epa.gov/storet/pptfiles/manning.ppt|url-status=dead|archive-date=July 11, 2004|title=An overview of the history of development of the EPA STORET System, with some comments on future timelines and plans.|date=November 7, 2001|page=3|format=PPT}}</ref> one IBMer described this as "[getting] blood out of the turnip", and noted that "most didn't run MVT".<ref name="most-didnt-run-mvt"/>

Reasons for a 360/50 site to run MFT<ref>{{cite newsgroup|url=https://groups.google.com/forum/#!original/alt.folklore.computers/3H0Iz7lGHYE/_Gk2OHyKshoJ|title=Re: Price of core memory|author=Gerard S.|date=June 1, 2001|newsgroup=alt.folklore.computers|quote=We had to revert to MFT to get a 98K partition, plus a reader and writer.}}</ref> rather than MVT were:

Line 89 ⟶ 90:

==References==

{{Reflist}}

==External links==

*{{cite web |first=Ken |last=Shirriff |title=Simulating the IBM 360/50 mainframe from its microcode |date=January 2022 |url=http://www.righto.com/2022/01/ibm360model50.html}}

{{IBM System/360 line}}