IBM System/360 Model 30: Difference between revisions

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

{{Infobox information appliance

| name = IBM System/360 Model 30

| title = IBM System/360 Model 30

| aka =

| logo logo_size = File:IBM logo.svg120px

| image_size = 270px

| logo = File:IBM Logo 1956 1972.svg

| image = File:IBM System360 Model 30.jpg

| caption = IBM System/360 Model 30 at the [[Computer History Museum]]

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==History==

The Model 30 was a popular [[IBM mainframe]] which was announced in 1964 across the world as the then least powerful of the [[IBM System/360|System/360]]s.<ref –group=NB>The less powerful [[IBM System/360 Model 20|Model 20]], offered only partial compatibility with the rest of the System/360 line.</ref> The System/360 series was the first line of computers in the world to allow machine language programs to be written that could be used across a broad range of compatible machines of different sizes. It was the smallest model that had the full [[System/360]] instruction set (unlike the [[IBM System/360 Model 20|Model 20]]) and served as a stand-alone system, communications system or as a satellite processor of a larger system.<ref name="ibm-archives">{{cite web|title=IBM Archives: System/360 Model 30|url=https://www-03.ibm.com/ibm/history/exhibits/mainframe/mainframe_PP2030.html|website=IBM|accessdatedate=1623 AugustJanuary 20162003|archive-url=https://web.archive.org/web/20230327055011/https://www.ibm.com/ibm/history/exhibits/mainframe/mainframe_PP2030.html|archive-date=2023-03-27|url-status=dead}}</ref>

The first delivery of the 360/30 was in June 1965 to [[McDonnell Aircraft]].<ref name=ibmbook>{{cite book|last1=Pugh|first1=Emerson W.|last2=Johnson|first2=Lyle R.|last3=Palmer|first3=John H.|title=IBM's 360 and early 370 systems|url=https://archive.org/details/ibms360early370s0000pugh|url-access=registration|date=1991|publisher=MIT Press|___location=Cambridge, Mass.|isbn=9780262161237}}</ref>

Along with the [[IBM System/360 Model 40|360/40]], these were the two largest revenue producing [[IBM System/360#SummaryTable of modelsSystem/360 shippedmodels|System/360 models]],<ref name=ibmbook/> accounting for over half the System/360 units sold.<ref>An [[Automatic Data Processing|ADP]] Newsletter cited on page 56 in {{cite book|editor-last1=Weiss|editor-first1=Eric A. (ed)|title=Computer Usage Essentials|date=1969|publisher=McGraw-Hill|lccn=71-76142}} shows sales of the 360 Model 30 (36%) and the Model 40 (22.6%), for a total of 58.6%</ref>

==Models==

[[File:IBM System 360 model 30 profile.agr.jpg|thumb|closeup (profile) of 360/30 Console]]

Four models<ref group='NB'>Lower case "M"</ref> of the 360/30 were initially offered.<ref name="mod30-func-char">{{cite book|url=http://www.bitsavers.org/pdf/ibm/360/funcCharfunctional_characteristics/GA24-3231-7_360-30_funcChar.pdf|title=IBM System/360 Model 30 Functional Characteristics|id=GA24-3231-7|date=August 1971}}</ref> They vary by the amount of [[Magnetic-core memory|core memory]] with which the system was offered. The C30, D30, E30 and F30 were respectively configured with 8K, 16K, 32K and 64K of core memory.<ref name="mod30-func-char"/>{{rp|Fig.5, p.9}}

It was little publicized that there were two versions of the Model 30,<ref name="mod30-func-char"/>{{rp|pp.2,8,9}} known (on the rare occasions when they were distinguished at all) as the 30-1 and the 30-2. The original 30-1 had a 2.0 microsecond storage cycle. Later, after the first 1000 30-1 were shipped,<ref name= ibmbook/> it was replaced by the 1.5-microsecond 30-2, although the 30-1 was silently retained in the sales catalog. The two were cosmetically different; the 30-1 looked like other System/360 models, with indicator lamps exposed on the front panel and labeled, but the 30-2 took a retrograde design step, putting the lights behind a stencil, as they had been on pre-360 machines like the [[IBM 1401]].

The (faster) 30-2 had an additional model, DC30, with 24K of memory.<ref name="mod30-func-char"/>{{rp|Fig.4, p.9}}

The 7th edition of IBM System/360 Basic Operating System Programmer's Guide, dated September 1967, lists first among ''major changes'' support for "an intermediate storage size (24K) for System/360 Model 30."<ref name="BOS_ProGuide">{{cite book|url=http://bitsavers.trailing-edge.com/pdf/ibm/360/bos_bps/C24-3372-6_BOSpgmr_Sep67.pdf|title=IBM System/360 Basic Operating System Programmer's Guide|id=C24-3372-6|date=September 1967|publisher=IBM}}</ref>

===96K upgrade===

In response to competitive pressures, IBM introduced a memory upgrade option, allowing 96K on a 360/30.<ref>Historical Note: A posted submission to Ed Thelen's 360/30 writings (http://ed-thelen.org/comp-hist/ibm-360-30.html) signedfrom LEONARD.BEARES.ctrDecember (at)2005, disa.millabeled (December"Historical 2005)Note", indicated that, in response to a 128K offering by a small company, IBM actually introduced an upgrade, allowing 96K on a 360/30. BEARESThe author noted that this allowed hour-plus tape/disk-based sorts to be done in-core in minutes.</ref><ref>{{cite book|title=IBM System/360 Model 30 Storage Expansion Feature Manual: RPQ's EA3807, EA1527; or RPQ's Y91283 and Y91325 (World Trade)|id=GA24-3564}}</ref> It seems, based on the system's front panel, that a provision for supporting more than 64K had been pre-planned.<ref>http://www.ljw.me.uk/ibm360/links has an entry named '''Glenn's Computer Museum''' (http://www.glennsmuseum.com/ibm/ibm.html) that has the following annotation: note that this front panel has indicators for extra address bits to allow more than 64k main storage</ref>

==Microcode==

The Model 30 [[CPU]] used an 8-bit [[microarchitecture]] with only a few [[hardware register]]s; everything that the programmer saw was

[[Emulator|emulated]] by the [[microprogram]].<ref name="30theory">{{cite book|url=http://bitsavers.org/pdf/ibm/360/fe/2030/Y24-3360-1_2030_FE_Theory_Opns_Jun67.pdf|title=Field Engineering Theory of Operation, 2030 Processing Unit, System/360 Model 30|id=Y24-3360-1|edition=Fifth|date=June 1967|publisher=IBM}}</ref><ref>{{cite book|url=http://bitsavers.org/pdf/ibm/360/fe/2030/Model_30_Microprogramming_Lang.pdf|title=Model 30 Microprogramming Language|publisher=IBM}}</ref> Handling a 4-byte word took (at least) 6 microseconds, based on a 1.5 microsecond storage access cycle time.<ref name="30theory"/>{{rp|pg.1–4}}

The microcode was stored in [[CCROS]] (Card Capacitor Read-Only Storage) developed in Endicott. The Model 30 and Model 40 were originally supposed to share the [[Transformertransformer Read Onlyread-only Storagestorage]] (TROS) being developed at [[IBM Hursley]], but CCROS was cheaper to manufacture.<ref name= ibmbook/> This system used [[Mylar]] cards the size and shape of a standard IBM [[punched-card]], so the microcode could be changed using a [[keypunch]]. Each card held 720 bits, and the total microcode consisted of 4032 60-bit words. The Mylar "encased copper tabs and access lines."<ref name="encyc">{{cite book |editor-last1=Kent (ed.) |editor-first1=Allen |title=Encyclopedia of Library and Information Science: Volume 69 - Supplement 32 |date=2000 |publisher=CRC Press |isbn=0-8247-2069-5 |page=267 |url=https://books.google.com/books?id=1U_gOuKGFYYC&pg=PA267 |accessdateaccess-date=Dec 3, 2018}}</ref> A hole punched at a specific ___location removed the copper tab and encoded a zero, unpunched locations were read as ones.<ref name="encyc"/>

[[File:Ibm 360-30.jpg|thumb|IBM 360 Model 30 front panel and internal components]]

==System configuration==

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! colspan="2" | A typical, early, basic Model 30 system had the following configuration:<ref>{{cite book|url=http://bitsavers.org/pdf/ibm/360/operatingGuide/C20-1635-2_Model_40_Operating_Techniques.pdf|title=IBM System/360 Model 40 Operating Techniques|id=C20-1635-2|publisher=IBM}}</ref>

|-

| style="vertical-align: top;" |Model 30 processor ||IBM 2030 Central Processing Unit<br>*32&nbsp;KB storage<br>*storage protection feature<br>*standard instruction set<br>*decimal instruction set<ref group=NB>Optional floating-point instruction set was also available</ref><br>*one multiplexor channel<br>*one selector channel<br>*interval timer

|-

|Operator console ||[[IBM 1052]] Typewriter-Keyboard (usually assigned to 01F hexadecimal address)

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|Tape storage || two [[IBM 2415]] Magnetic Tape Units (180 & 181)

|}

[[File:IBM 360-30.jpg|thumb|210x210px|IBM 360 Model 30 front panel closeup]]

To keep costs down, CPU features such as the interval timer and storage-protection feature were optional.

==System software==

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* '''DOS''' - Disk Operating System

BPS [[IBM Basic Programming Support|(Basic Programming Support)]] did not require a disk drive or tape drive. It was introduced in 1965, and has been described<ref name="DeMorton">{{cite web|url=http://www.demorton.com/Tech/$OSTL.pdf|title=IBM Mainframe Operating Systems: Timeline and Brief Explanation For the IBM System/360 and Beyond|author=Dave Morton|date=April 2015|access-date=2016-09-22|archive-url=https://web.archive.org/web/20140701185435/http://www.demorton.com/Tech/$OSTL.pdf|archive-date=2014-07-01|url-status=dead}}</ref> as "primarily a set of utilities and compilers (that) existed on cards only."<ref name="DeMorton"/>{{rp|pages 10,18}}

BOS [[BOS/360|(Basic Operating System)]] required a disk drive, but, like BPS, could run on the smallest 360/30, the 8K model C30.<ref name="BOS_ProGuide"/>{{rp|pp.9,10}}

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The minimum memory needed to run DOS or TOS was 16&nbsp;KB.

TOS [[TOS/360|(Tape Operating System)]], as the name suggests, required a tape drive but no disk. It shared most of the code base<ref name=40Y.mem>{{cite newsgroup|url=https://groups.google.com/d/msg/alt.folklore.computers/RZA6FD27Tc0/-LoIXsOee7gJ|title=DOS/360: Forty years|author=Joe Morris|newsgroup=alt.folklore.computer|date=April 25, 2005|quote=Don't forget TOS, the bastard cousin of DOS. Either could be generated from the same set of distribution libraries...}}</ref> and some manuals<ref>{{cite web|url=http://www.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|date=October 1970|id=GC2ij-5030-8}}</ref><ref>{{cite web|url=http://www.bitsavers.org/pdf/ibm/360/dos/GC24-3465-8_DOS_and_TOS_Utility_Programs_R26.1_Aug73.pdf|title=DOS and TOS Utility Programs|date=August 1973|id=GC24-3465-8}}</ref> with IBM's DOS/360 and went through 14 releases. TOS was discontinued<ref>{{cite mailing list|url=https://www.mail-archive.com/ibmvm (at) @listserv.uark.edu/msg24371.html|author=Anne and Lynn Wheeler|title=Re: IBM 1401|date=May 28, 2009|mailing-list=[e-mail]}}</ref>{{failed verification|date=January 2020}} when disk drives became more affordable.<ref>Computerworld, Sept. 5, 1977, p.40 - quotes an IBM task force report that referred to "price alone rather than by price/performance."</ref>

DOS [[DOS/360|(Disk Operating System)]] was a popular choice for the 360/Model 30.<ref>Of those 360/Model 30 and 360/Model 40 machines still around in 1981/being replaced by 4300 systems, a Computerworld survey showed that DOS was what they ran/had run, May 25, 1981, p. 26</ref><ref>{{cite web|url=http://www.edwardbosworth.com/My3121Textbook_HTM/MyText3121_Ch03_V01.htm|title=Programming Assembler Language on the IBM Mainframes: An Introduction|at=Chapter 3 – The Heritage of the IBM System/360|author=Edward L. Bosworth}}</ref><ref>{{cite web|url=http://ed-thelen.org/comp-hist/ibm-360-30.html|title=IBM System 360, Model 30|author=Ed Thelen}}</ref><ref>{{cite web|url=http://www.highersystems.co.uk/ibm_360_30.html|title=IBM 360/30|access-date=2016-10-05|archive-date=2016-07-07|archive-url=https://web.archive.org/web/20160707135313/http://highersystems.co.uk/ibm_360_30.html|url-status=dead}}</ref>

Amazingly<ref group='NB'>The source cited prefixes its statement with "Amazing fact:"</ref> the smaller BOS had a [[Spoolingspooling]] system for queued printing,<ref>{{cite book |last1=IBM Corporation |title=IBM System/360 Basic Programming Support and IBM Basic Operating System/360 Programming Systems Summary |date=1965 |url=https://bitsavers.org/pdf/ibm/360/bos_bps/C24-3420-0_BPS_BOS_Programming_Systems_Summary_Aug65.pdf |access-date=June 15, 2024}}</ref>{{rp|p.9}} whereas DOS did not<ref name="DeMorton"/>{{rp|page 18}} until the arrival in the late 1960s of "an add-on component called POWER."<ref name="DeMorton"/>{{rp|page 16}}

==Programming languages==

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==Compatibility features==

The ability to continue running programs designed for earlier systems was crucial to selling new hardware.<ref>{{cite book|title=The Technical and Social History of Software Engineering|author=Capers Jones|date=21 November 2013 |isbn=0133365891978-0133365894}}</ref> Although the instruction set of System/360 was not [[Backward compatibility|backward compatible]] with earlier systems,<ref>Computerworld, April 24, 1989, page 1</ref> IBM provided [[emulator]]s for the earlier systems.

===IBM 1400 series emulation===

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===IBM 1620 emulation===

Although the 360/30 could be configured to emulate an [[IBM 1620]],<ref name="mod30-func-char"/>{{rp|p.11}} two factors made it less crucial than the above IBM 1400 series emulation:

* The [[IBM 1130]] was the preferred successor to the IBM 1620.<ref>{{cite book|title=Milestones in Computer Science and Information Technology|url=https://archive.org/details/milestonesincomp0000reil|url-access=registration|author=Edwin D. Reilly|year=2003|isbn=1573565210}}</ref><ref>{{cite book|title=History of Computer Graphics|author=Dan Ryan|isbn=1456751158|series=DLR Associates Series}}</ref>

* [[Fortran]] accounted for a significant part of how the 1620 was used,<ref>{{cite book|title=Basic Programming Concepts and The IBM 1620 Computer|author1=Daniel N. Leeson|author2=Donald L. Dimitry|year=1962|publisher=Holt, Rinehart and Winston}}</ref> and IBM 1620 Fortran programs could be converted to run on System/360.

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{{DEFAULTSORT:IBM System 360 Model 30}}

[[Category:IBM System/360 mainframe line|System/ 360 Model 30]]

[[Category:Computer-related introductions in 1964]]