IBM System/370 Model 145

The IBM System/370 Model 145 was announced September 23, 1970,[1] three months after the 155 and 165[2] models. It was the fourth member of the IBM System/370 line of computers,[3] and was the first IBM computer to use semiconductor memory for its main memory instead of magnetic core memory.[4] It was described as being five times faster than the IBM System/360 Model 40. First shipments were scheduled for late summer of 1971.[1]

IBM System/370 Model 145
IBM System/370 Model 145
ManufacturerInternational Business Machines Corporation (IBM)
Product familySystem/370
GenerationThird
Release dateSeptember 23, 1970 (1970-09-23)
Introductory price$705,775 to $1,783,000
Memorysemiconductor (first IBM use for main memory), 112–512 KB
StorageIBM 3330, IBM 2319
Backward
compatibility		IBM System/360, IBM 1400 series, IBM 7010
WebsiteOfficial website IBM Archives
IBM System/370 Model 145 system console
IBM monolithic memory card

New capabilities

The System/370's basic architecture was described as having been an extension, but not a redesign, from that of IBM's 1964-introduced System/360.[2]

The 370 introduced some new instructions, such as

  • MOVE CHARACTER LONG (MVCL) and
  • COMPARE CHARACTER LONG (CLCL),

thereby permitting operations on up to 224-1 bytes (16 MB), vs. the 256-byte limits on the 360's MVC and CLC,[5][6] but lacked a DAT (Dynamic Address Translation) box.

Virtual memory

Some said about the 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."[7]

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,[7] the 145's customers had two advantages:

  • 370/145 customers did not have to wait as long for this lack of virtual memory to be remedied[NB 1]
  • there was no need to buy extra hardware: An upgrade to the 145's microcode through a new microcode floppy disk[8] enabled virtual memory capability.

VM/CMS

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

See also

Notes
  1. June 1971 vs. Aug. 1972

References
  1. "System/370 Model 145". IBM Archives. IBM.
  2. "System/370 Model 165". IBM Archives. IBM.
  3. A third 370, the 370/195, had separately been announced the same day as the 155 & 165. The new 195 came 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
  4. William D. Smith (September 24, 1970). "A new computer unveiled by I.B.M". The New York Times.
  5. http://faculty.cs.niu.edu/~byrnes/csci360/notes/360ex.htm
  6. http://research.microsoft.com/en-us/um/people/gbell/tcmwebpage/timeline/chap51_ibm370_cs2.pdf
  7. "What Course for the 3081?". Computerworld. November 24, 1980. p. 34.
  8. IBM Maintenance Library 3145 Processing Unit Theory - Maintenance. IBM. pp. CPU 117–129. SY24-3581-2
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