IBM System/370 Model 155: Difference between revisions

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{{Infobox information appliance

[[File:IBM_magnetic_disk_drives_3330+3333.png|thumb|The IBM 3330 <br>Direct Access Storage Facility, <br>code-named Merlin, was introduced in June 1970 for use with the IBM System/370. Its removable disk packs could hold 100 MB]]

*| name = [[IBM System/370 Model 145]]155

The '''IBM System/370 Model 155''' (and the [[IBM System/370 Model 165|Model 165]]),<ref name=IBMarc.165>{{cite web|url=https://www-03.ibm.com/ibm/history/exhibits/mainframe/mainframe_PP3165.html|title=System/370 Model 165|website=IBM Archives|publisher=IBM}}</ref>

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were jointly announced Jun 30, 1970.<ref name=IBMarc.155>{{cite web|url=https://www-03.ibm.com/ibm/history/exhibits/mainframe/mainframe_PP3155.html|title=System/370 Model 155|website=IBM Archives|publisher=IBM}}</ref><ref>the same day as the announcement of the 370/195, coming about 14 months after the announcement of the 360/195. Both 195 machines were withdrawn Feb. 9, 1977. see https://www-03.ibm.com/ibm/history/exhibits/mainframe/mainframe_PP2195.html and https://www-03.ibm.com/ibm/history/exhibits/mainframe/mainframe_PP3195.html</ref>

| aka =

| logo = File:IBM logo.svg

| image = IBM System370 Model 155 in Teamco a.s. & Co (1).jpg

*| caption = [[IBM System/370 Model 165]]155

| developer =

| manufacturer = International Business Machines Corporation ([[IBM]])

| family = [[System/370]]

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| releasedate = {{Start date|1970|06|30}}

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| discontinued = December 23, 1977

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| website = {{Official website|https://www-03.ibm.com/ibm/history/exhibits/mainframe/mainframe_PP3155.html}} ''IBM Archives''

}}

[[File:IBM_magnetic_disk_drives_3330+3333.png|thumb|The IBM 3330 <br>Direct Access Storage Facility, <br>code-named Merlin, was introduced in June 1970 for use with the IBM System/370. Its removable disk packs could hold 100 &nbsp;MB]]

==Limitations==

Some said about these early members of the [[IBM System/370]] family, looking back, that they were not "the real 370 line" because

"neither offered virtual storage capability, which was to be a hallmark of the 370 line."<ref name="what-course-for-the-3081">{{cite newspaper|newspaper=Computerworld|date=November 24, 1980|page=34|url=https://books.google.com/books?id=cKmJJd7R8PIC&pg=PA34#v=onepage&q&f=false|title=What Course for the 3081?}}</ref>

The '''IBM System/370 Model 155''' (and the [[IBM System/370 Model 165|Model 165]]),<ref name=IBMarc.165>{{cite web|url=https://www-03.ibm.com/ibm/history/exhibits/mainframe/mainframe_PP3165.html|title=System/370 Model 165|website=IBM Archives|date=23 January 2003|publisher=IBM|archive-url=https://web.archive.org/web/20230729090329/https://www.ibm.com/ibm/history/exhibits/mainframe/mainframe_PP3165.html|archive-date=2023-07-29|url-status=dead}}</ref>

The 370/155 was described as able to "run under [[DOS/360 and successors|DOS]]." Both the 155 and the larger 370/165 could "run under [[OS/360 and successors|OS/360]]." Neither machine, as announced, could run a virtual memory operating system.

were jointly announced Jun 30, 1970<ref name=IBMarc.155>{{cite web|url=https://www.ibm.com/ibm/history/exhibits/mainframe/mainframe_PP3155.html|title=System/370 Model 155|website=IBM Archives|date=23 January 2003|publisher=IBM|archive-url=https://web.archive.org/web/20230516082850/https://www.ibm.com/ibm/history/exhibits/mainframe/mainframe_PP3155.html|archive-date=2023-05-16|url-status=dead}}</ref> as "designed for ... the Seventies." That same day [[IBM]] announced the 370/195.<ref>{{cite web|url=https://www.ibm.com/ibm/history/exhibits/mainframe/mainframe_PP3195.html|title=System/370 Model 195|website=IBM Archives|date=23 January 2003|publisher=IBM|archive-url=https://web.archive.org/web/20230729090333/https://www.ibm.com/ibm/history/exhibits/mainframe/mainframe_PP3195.html|archive-date=2023-07-29|url-status=dead}}</ref> They were the first three models of the [[IBM System/370]] line of computers.

"neitherSince offerednone virtualof storagethem capabilitycame with [[virtual memory]], "which was to be a hallmark of the 370 line.",<ref name="what-course-for-the-3081">{{cite newspapernews|newspaper=Computerworld|date=November 24, 1980|page=34|url=https://books.google.com/books?id=cKmJJd7R8PIC&pg=PA34#v=onepage&q&f=false|title=What Course for the 3081?}}</ref> some said about these early members of the [[IBM System/370]] family, especially about the 155 and 165, that they were not "the real 370 line."<ref name="what-course-for-the-3081" />

==Growth path==

The initially announced systems were in many ways merely improved [[IBM System/360|IBM 360]] systems. Both were announced as

running 360 [[Operating System]]s.<ref group="NB">DOS on the 155, MFT or MVT on either machine</ref> No mention was made of [[virtual memory]]

or new operating systems.

Three months later a fourth IBM System/370, the [[IBM System/370 Model 145|Model 145]], was announced.

The IBM System/360 architecture was described as having been "extended, but not redesigned, for System/370."<ref name=IBMarc.165/>

===UpgradeVirtual option=memory==

The initially announced System/370 Models 155 and 165 systems did not support virtual memory.

In 1972 an upgrade option was announced "to provide the hardware necessary to operate in a virtual memory mode."<ref>{{cite newspaper|newspaper=Computerworld|date=August 15, 1973|page=17|title=First IBM DAT Box Installed|url=https://books.google.com/books?id=T3qky0Z-gc0C&pg=PA17#v=onepage&q&f=false}}</ref>

wait untilIn 1972 an upgrade option was announced "to provide the hardware necessary to operate in a virtual memory mode."<ref>{{cite news|newspaper=Computerworld|date=August 15, at1973|page=17|title=First IBM DAT Box Installed|url=https://books.google.com/books?id=T3qky0Z-gc0C&pg=PA17}}</ref> Unlike the [[IBM System/370 Model 145]], which timeas early as June 1971 included the hardware necessary to support virtual memory, and for which a [[microcode]] update from a floppy disk, adding support for virtual memory, was announced in 1972, the Model 155 and Model 165 needed expensive hardware additions - $200,000 for the 155 and $400,000 for the 165 - to add virtual memory capability. theirAn upgraded 155 was known as an IBM System/370 Model 155-II.<ref>{{cite journal | author = A. Padegs | title = System/360 and Beyond | journal = IBM Journal of Research & Development | volume = 25 | issue = 5 | pages = 377–390 |date=September 1981 | publisher = IBM | doi = 10.1147/rd.255.0377}} &ndash; tables include model characteristics (Table 1) and announcement/shipment dates (Table 2). The S/370-155-II and -165-II are listed under the former but not the latter, because the upgraded systems were not formally announced as separate models. The "System/370 Advanced Function" announcement, including the -158 and -168, was the main public event.</ref>

Unlike [[IBM System/370 Model 145]] customers, who as early as June 1971 were able to merely add virtual memory capability with a simple [[microcode]] update from a floppy disk, those using what literature of the day at times called a "boat anchor" (if left as-is) needed to purchase expensive hardware<ref group="NB">$200,000 for the 155 and $400,000 for the 165</ref> to upgrade their machines, and even this had to

wait until 1972, at which time their upgraded 155 was known as an IBM System/370 Model 155-II.<ref>{{cite journal | author = A. Padegs | title = System/360 and Beyond | journal = IBM Journal of Research & Development | volume = 25 | issue = 5 | pages = 377–390 |date=September 1981 | publisher = IBM | doi = 10.1147/rd.255.0377}} &ndash; tables include model characteristics (Table 1) and announcement/shipment dates (Table 2). The S/370-155-II and -165-II are listed under the former but not the latter, because the upgraded systems were not formally announced as separate models. The "System/370 Advanced Function" announcement, including the -158 and -168, was the main public event.</ref>

==Physical memory==

Although the joint 155/165 announcement<ref name=IBMarc.165/> did not have the word virtual, there were multiple references to (physical) memory, storage (both main memory and disk storage), and [[cache memory]] under the name "buffer".

The 155 had seven main memory choices, ranging from 256&nbsp;KB to 2&nbsp;MB; the 165: five possibilities, from 512&nbsp;KB to 3&nbsp;MB. Both models were described as having "a very high-performance buffer storage backed by a large" main memory.

Another signs of not being "the real 370 line" is that the main storage in 3155 was not monolithic, it was using the older type of ferrite [[core storage]]. The 3360 storage unit could have 256 or 512&nbsp;KB of storage, each 3155 could have one to four 3360 units attached. Also, the microcode in 3155 was "hardwired" while later 370 systems loaded the microcode from a [[floppy disk]], enabling easy upgrades. The 3155 also had very limited error logging capability and used an [[IBM 3215]] typewriter console.

==Channels==

Channel 0 was a byte multiplexor channel, channel 1 to 5 were block multiplexor channels. Channel 0 and 1 were standard, channel 2 to 5 were optional upgrades.

==Operating systems==

The 370/155 supported both [[DOS/360 and successors|DOS/360]] and [[OS/360 and successors|OS/360]].<ref name=IBMarc.155 /> Being members of the System/370 family, the Model 155 and Model 165 were compatible with each other. Lacking virtual memory support, neither machine, as announced, could run a virtual memory operating system.

A 370/155 upgraded to a 370/155-II, with support for virtual memory added, supported [[DOS/VS]] (DOS/360 with virtual storage), [[OS/VS1]] ([[OS/360 and successors#OS/MFT|OS/360 MFT]] with virtual storage), OS/VS2 Release 1 ([[OS/360 and successors#OS/MVT|OS/360 MVT]] with virtual storage), termed [[OS/VS2 (SVS)|SVS]] (Single Virtual Storage), and Release 2, termed [[MVS]] (Multiple Virtual Storage), and [[VM (operating system)|VM/370]].

==See also==

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* [[IBM System/360]]

* [[IBM System/370]]

* [[IBM System/370 Model 145]]

* [[IBM System/370 Model 165]]

* [[IBM 3090]]

==Notes==

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==References==

{{reflist}}

{{IBM System/370 line}}

{{DEFAULTSORT:IBM System 370 Model 155}}

[[Category:IBM computers]]

[[Category:IBM System/360 mainframe line]]

[[Category:Computer-related introductions in 1970]]