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
Render of S/370 Model 145 with typical peripherals
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. 23 January 2003.
  2. "System/370 Model 165". IBM Archives. IBM. 23 January 2003.
  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.ibm.com/ibm/history/exhibits/mainframe/mainframe_PP2195.html and https://www.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. "Move Character Long". CSCI 360 Computer Programming in the Assembler Language.
  6. Case, Richard P.; Padegs, Andris. "Architecture of the IBM System/370" (PDF). In Bell, C. Gordon; Newell, Allen (eds.). Computer Structures: Readings and Examples.
  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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