IBM System/370 Model 135
ManufacturerInternational Business Machines Corporation (IBM)
Product familySystem/370
Release dateMarch 8, 1971 (1971-03-08)
DiscontinuedOctober 16, 1979
WebsiteOfficial website IBM Archives
IBM 3330

"Expanded channel capacity
and the ability to use the high-performance
IBM 3330 disk storage under either Operating System (OS)or Disk Operating System (DOS) were ... among the factors significant to the Model 135's ...capabilities."

The IBM System/370 Model 135 was announced March 8, 1971,[1] the only 370 introduced that year. The 135 was IBM's fifth System 370,[lower-alpha 1] and it was withdrawn October 16, 1979.

Special features

Although microcode was not a uniquely new feature at the time of the 135's introduction, having been used in most System/360 models and in most System/370 models introduced so far, the ability to upgrade a system's microcode without changing hardware, by storing the microcode in read-write memory rather than read-only memory, was not common at that time.[2][3]

The read-write memory containing the firmware was loaded from a "reading device located in the Model 135 console"; this allowed updates and adding features to the Model 135's microcode.[1] The "reading device" was a built-in (read-only) floppy disk drive.[4] The 145, introduced the prior year, also had this feature.[5]

Optional features

The Model 135 was the last of the 370s to be introduced without Virtual memory. Four of the five[lower-alpha 2] could be upgraded. Unlike the 155 & 165, which required an expensive[lower-alpha 3] hardware upgrade to add a DAT box (Dynamic Address Translation), the 135 & 145 [6] could obtain their virtual memory upgrades from a floppy disk.

Microcode upgrades were also available to add "user-selected options such as

An upgraded Model 135[7] was termed a 370/135-3[lower-alpha 5]

Customers of the 370/135 had a choice of four main memory sizes, ranging from 96K to 256K.

Other

  • The 370/135 was introduced as running "under either OS or DOS.[1] Newer versions thereof (DOS/VS and OS/VS1) and Virtual Machine Facility/370 (VM/370) subsequently became available options once the 135's microcode was upgraded to support virtual memory. This was priced at $120,000 and came with "increased reloadable control store in addition to some power units." The upgrade could be done "in the field" and the resultant system was now deemed a 370/135-3.[8]
  • The 135 was "partly developed at Hursley, UK."[9]

Images

See also

Notes

  1. ↑ of 11
  2. ↑ the 135, 145, 155 and 165, but not the 195
  3. ↑ $200,000 and $400,000 respectively
  4. ↑ (1401, 1440 and 1460)
  5. ↑ and the upgrade could be done "in the field."

References

  1. 1 2 3 4 "System/370 Model 135". IBM Archives. IBM. 23 January 2003.
  2. ↑ Padegs, A. (September 1981). "System/360 and Beyond". IBM Journal of Research & Development. IBM. 25 (5): 377–390. doi:10.1147/rd.255.0377. In the initial System/360 models, microprograms resided in read-only storage, but in most later models read-write storage is used. - tables include model characteristics (Table 1) and announcement/shipment dates (Table 2). The S/370-155-II and -165-II are listed under the former but not the latter, because the upgraded systems were not formally announced as separate models. The "System/370 Advanced Function" announcement, including the -158 and -168, was the main public event.
  3. ↑ "DOS/360: Forty years". Newsgroup: alt.folklore.computers. May 16, 2005. Retrieved 2023-10-02. No, you'll find no IMPL button on a System/360 Model 30. It's control store was Card Capacitive ROS. System/360's used a variety of read only control stores, so changing the microcode meant replacing parts (e.g., with parts that were personalized by punching holes in a card). Later models like the 85 and 25 had writable contol stores, the 85 using a volatile SRAM array and the 25 using a part of core memory.
  4. ↑ "Floppy Disks - CHM Revolution". www.computerhistory.org. Retrieved 2021-06-09.
  5. ↑ http://www.computerhistory.org/timeline/1968/#169ebbe2ad45559efbc6eb357200edaf describes it as an 80K 8-inch floppy.
  6. ↑ IBM Maintenance Library 3145 Processing Unit Theory - Maintenance (PDF) (Fifth ed.). IBM. p. CPU 139. SY24-3581-4.
  7. ↑ Computerworld. IDG Enterprise. 1976-07-05.
  8. ↑ "Users May Have Jump on Upgrades". Computerworld. July 5, 1976. p. 2.
  9. ↑ "Some Key Dates in IBM's Operations in Europe, the Middle East, Asia" (PDF). IBM.
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