View source for IBM System/370 Model 145

{{Infobox information appliance
| name         = IBM System/370 Model 145
| title        = 
| aka          = 
| logo_size    = 120px
| image_size   = 270px
| logo         = File:IBM logo.svg
| image        = File:1968 CNRZ mécanographie-6-cliche Jean Weber.jpg 
| caption      = IBM System/370 Model 145
| developer    = 
| manufacturer = International Business Machines Corporation ([[IBM]])
| family       = [[System/370]]
| generation   = Third
| releasedate  = {{Start date|1970|09|23}}
| lifespan     = 
| price        = $705,775 to $1,783,000
| discontinued =
| unitssold    = 
| unitsshipped = 
| media        = 
| os           = 
| power        = 
| soc          = 
| cpu          = 
| memory       = [[semiconductor memory|semiconductor]] (first IBM use for main memory), 112–512 KB
| storage      = [[IBM 3330]], [[IBM 2319]]
| memory card  = 
| display      = 
| graphics     = 
| sound        = 
| input        = 
| controllers  = 
| camera       = 
| touchpad     = 
| connectivity = 
| platform     = 
| service      = 
| dimensions   = 
| weight       = 
| topgame      = 
| compatibility= [[IBM System/360]], [[IBM 1400 series]], [[IBM 7010]]
| predecessor  = 
| successor    = 
| related      = 
| website      = {{Official website|https://www.ibm.com/ibm/history/exhibits/mainframe/mainframe_PP3145.html}} ''IBM Archives''
}}
[[File:Hist. Rechenzentrum.png|thumb|Render of S/370 Model 145 with typical peripherals]]
[[File:Panel_370-145.png|thumb|IBM System/370 Model 145 system console]]
 [[File:IBM monolithic memory card.jpg|thumb|IBM monolithic memory card]]
The '''IBM System/370 Model 145''' was announced September 23, 1970,<ref name=IBMarc.145>{{cite web|url=https://www.ibm.com/ibm/history/exhibits/mainframe/mainframe_PP3145.html|title=System/370 Model 145|website=IBM Archives|date=23 January 2003 |publisher=IBM|archive-url=https://web.archive.org/web/20230729090334/https://www.ibm.com/ibm/history/exhibits/mainframe/mainframe_PP3145.html|archive-date=2023-07-29|url-status=dead}}</ref> three months after the [[IBM System/370 Model 155|155]] and [[IBM System/370 Model 165|165]]<ref name=IBMarc.165>{{cite web
   |url=https://www.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> models.  It was the fourth member of the [[IBM System/370]] line of computers,{{efn|A third 370, the 370/195, had separately been announced the same day as the 155 & 165.<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>}} and was the first IBM computer to use [[semiconductor memory]] for its main memory instead of [[magnetic core memory]].<ref>{{cite news  |newspaper=[[The New York Times]]
   |url=https://www.nytimes.com/1970/09/24/archives/a-new-computer-unveiled-by-ibm-main-memory-system-uses.html
   |title=A new computer unveiled by I.B.M
   |author=William D. Smith  |date=September 24, 1970}}</ref> It was described as being five times faster than the [[IBM System/360 Model 40]]. First shipments were scheduled for late summer of 1971.<ref name=IBMarc.145 />

==Virtual memory==
Initially, the System/370 Model 145 did not support virtual memory.

Unlike the earlier Model 155 and 165 systems, for which an upgrade to [[virtual memory]] required the purchase of an expensive upgrade to add a DAT box,<ref name="what-course-for-the-3081">{{cite news|newspaper=Computerworld|date=November 24, 1980|page=34|url=https://books.google.com/books?id=cKmJJd7R8PIC&pg=PA34|title=What Course for the 3081?}}</ref> the Model 145 already included an associative memory<ref name=SY24-3581-1>{{cite book
 | title     = IBM Maintenance Library 3145 Processing Unit Theory - Maintenance
 | edition   = Second
 | url       = http://www.bitsavers.org/pdf/ibm/370/fe/3145/SY24-3581-1_3145_Processing_Unit_Theory-Maintenance_Oct71.pdf
 | id        = SY24-3581-1
 | date      = October 1971
 | publisher = IBM
 | pages     = CPU 117–129}}</ref><ref name=SY24-3581-4>{{cite book
 | title     = IBM Maintenance Library 3145 Processing Unit Theory - Maintenance
 | edition   = Fifth
 | url       = http://www.bitsavers.org/pdf/ibm/370/fe/3145/SY24-3581-4_3145_Processor_Theory_Maintenance.pdf
 | id        = SY24-3581-4
 | publisher = IBM}}</ref>{{rp|CPU 117-CPU 129}} used by the [[microcode]] for the DOS compatibility feature from its first shipments in June 1971;<ref name=SY24-3581-1/> the same hardware was used by the microcode for DAT.<ref name=SY24-3581-4 />{{rp|CPU 139}} Although IBM famously chose to exclude virtual storage from the S/370 announcement, that decision was being reconsidered during the completion of the 145 engineering, partly because of virtual memory experience at CSC and elsewhere. The 145 microcode architecture simplified the addition of virtual storage, allowing this capability to be present in early 145s without the extensive hardware modifications needed in other models. However, IBM did not document the 145's virtual storage capability, nor annotate the relevant bits in the control registers and PSW that were displayed on the operator control panel when selected using the roller switches. The Reference and Change bits of the Storage-protection Keys, however, were labeled on the rollers, a dead giveaway to anyone who had worked with the earlier 360/67. Existing S/370-145 customers were happy to learn that they did not have to purchase a hardware upgrade in order to run DOS/VS or OS/VS1 (or OS/VS2 Release 1 &ndash; which was possible, but not common because of the limited amount of main storage available on the S/370-145).

This resulted in two advantages of the 145 over the 155 and 165:
*  370/145 customers did not have to wait as long for this lack of virtual memory to be remedied{{efn|June 1971 vs. Aug. 1972}}
*  there was no need to buy extra hardware: An upgrade to the 145's [[microcode]] through a new microcode floppy disk<ref>IBM Maintenance Library 3145 Processing Unit Theory - Maintenance. IBM. pp. CPU 117–129. SY24-3581-2</ref> enabled virtual memory capability.

===Operating systems===
The 370/145 supported both [[DOS/360 and successors|DOS/360]] and [[OS/360 and successors|OS/360]].<ref name=IBMarc.145 /> Lacking virtual memory support, the 145, as announced, could not run a virtual memory operating system.

Upon gaining virtual memory capability via a microcode update, the 145 could now support the [[VM (operating system)|VMF (Virtual Machine Facility)]] and [[Conversational Monitor System|VM/CMS]], a [[time-sharing]] system.

==See also==
* [[List of IBM products]]
* [[IBM System/360]]
* [[IBM System/370]]

==Notes==
{{notelist}}

==References==
{{reflist}}

{{IBM System/370 line}}

{{DEFAULTSORT:IBM System 370 Model 145}}
[[Category:IBM System/360 mainframe line]]
[[Category:Computer-related introductions in 1970]]