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IBM System/370 Model 155

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The IBM 3330
Direct Access Storage Facility,
code-named Merlin, was introduced in June 1970 for use with the IBM System/370. Its removable disk packs could hold 100 MB

The IBM System/370 Model 155 (and the Model 165),[1] were jointly announced Jun 30, 1970.[2][3]

Limitations

Some said about these 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."[4]

The 370/155 was described as able to "run under DOS." Both the 155 and the larger 370/165 could "run under OS/360." Neither machine, as announced, could run a virtual memory operating system.

Growth path

The initially announced systems were in many ways merely improved IBM 360 systems. Both were announced as running 360 Operating Systems[NB 1]. No mention was made of virtual memory or new operating systems.

The IBM System/360 architecture was described as having been "extended, but not redesigned, for System/370."[1]

The 370 introduced some new instructions, such as MOVE CHARACTER LONG (MVCL) and COMPARE CHARACTER LONG (CLCL), thereby permitting operations on up to 2^24-1 bytes (16 MB), vs. the 256-byte limits on the 360's MVC and CLC.[5] [6], but lacked a DAT box.

Upgrade option

In 1972 an upgrade option was announced "to provide the hardware necessary to operate in a virtual memory mode."[7]

Unlike IBM System/370 Model 145 customers, who as early as June 1971 were able to merely add virtual memory capability with a simple microcode update from a floppy disk, those using what literature of the day at times called a "boat anchor" (if left as-is) needed to purchase expensive hardware[NB 2] to upgrade their machines, and even this had to wait until 1972, at which time their upgraded 155 was known as an IBM System/370 Model 155-II.[8]

See also

Notes

  1. ^ DOS on the 155, MFT or MVT on either machine
  2. ^ $200,000 for the 155 and $400,000 for the 165

References

  1. ^ a b "System/370 Model 165". IBM Archives. IBM.
  2. ^ "System/370 Model 155". IBM Archives. IBM.
  3. ^ the same day as the announcement of the 370/195, coming 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 Both 195 machines were withdrawn Feb. 9, 1977.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. ^ "What Course for the 3081?". Computerworld. November 24, 1980. p. 34.
  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. ^ "First IBM DAT Box Installed". Computerworld. August 15, 1973. p. 17.
  8. ^ A. Padegs (September 1981). "System/360 and Beyond". IBM Journal of Research & Development. 25 (5). IBM: 377–390. doi:10.1147/rd.255.0377. – 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.
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