IBM System/370 Model 148

The IBM System/370 Model 148 (and the Model 138[1]) were both announced June 30, 1976[2]

IBM System/370 Model 148
ManufacturerInternational Business Machines Corporation (IBM)
Product familySystem/370
Release dateJune 30, 1976 (1976-06-30)
DiscontinuedNovember 1, 1983
MemoryOne or two megabytes of high-density integrated monolithic processor storage
WebsiteOfficial website IBM Archives

Not only were they both more powerful and better in price/performance than their virtualized[3] counterparts, but actually much lower in price[4][5]

The 148 and 138,[6] both of which were withdrawn November 1, 1983, were marketed as followups for those wishing to upgrade, respectively, their 370/145 and 370/135 systems.

Expanded capabilities

The 148 had four times the reloadable control storage of the 145,[7] enabling or enhancing features such as:

  • APL Assist[8]
  • Extended control program support - going beyond the language-specific APL Assist, this had wider scope, reducing CPU cycles needed to run the operating system.[9]

A new model of the IBM 3203 printer family, the Model 4, was announced. Rated at 1200 Lines/Minutes, it was intended to provide already-available 1200 LPM printing, but in a more compact form.

Field upgrades

Sometimes known as in-the-field upgrades,[10] this is a capability that even recently was not universal.[11]

IBM could upgrade a 370/145 that had been field-upgraded to a 145-2, resulting in a 145-3. This was a major accomplishment, compared to what is known as a "forklift upgrade" - out with the old, in with the new, often consuming valuable time.[12] [13]

Marketing considerations

An industry research firm said "may be described as early 380s programmed to act like 370s"[4]

See also


  1. "System/370 Model 138". IBM Archives. IBM.
  2. "System/370 Model 148". IBM Archives. IBM.
  3. 135-3, 145-3
  4. "IBM 370/138, 148 Really 'Early 380s'? Users May Have Jump on Upgrades". Computerworld. July 5, 1976. p. 2.
  5. $350,000 for a 138 having 500K of memory, vs. $721,500 for a 135-3 with 500K - less than half the price!
  6. described as "mediumpowered System/370 computers" "I.B.M. Cutting Prices 20% on 2 Computers". The New York Times. March 2, 1978.
  7. 128K vs. 32K
  8. a Microcode-based feature that allowe for faster execution than a software-only approach.
  9. up to 20% for OS/VS1, up to 55% for VM/CMS.
  10. "Is it possible to upgrade a bCX1-R to a bCX1-CR in the field? (upgrade router to controller / router)" -
  11. "I am in the early stages of designing the TMS320F28377S into a new product and I would like to build in the field upgrade capability..." -
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