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
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
IBM System/360, IBM 1400 series, IBM 7010
WebsiteOfficial website IBM Archives

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


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.


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


  1. June 1971 vs. Aug. 1972


  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 Both 195 machines were withdrawn Feb. 9, 1977.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 and
  4. William D. Smith (September 24, 1970). "A new computer unveiled by I.B.M". The New York Times.
  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
This article is issued from Wikipedia. The text is licensed under Creative Commons - Attribution - Sharealike. Additional terms may apply for the media files.