4. From Tom Van Vleck's notes on the IBM 360/67 and CP/CMS Tom Van Vleck

posted Sep 13, 2010, 10:11 AM by Jeff Ogden   [ updated Dec 22, 2011, 11:45 AM ]
From http://www.multicians.org/thvv/360-67.html:

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Melinda Varian, in her outstanding memoir VM and the VM Community, tells how IBM didn't respond to the MIT Project MAC request for a next-generation timesharing machine in 1964. She tells how, too late, Gerry Blauuw of IBM made a proposal to Project MAC for a machine with some virtual memory features; and how the IBM Cambridge Scientific Center, located in Tech Square on the third floor, created the 44MPS and CP/CMS in the mid-60s.

When MIT and then Bell Labs chose GE machines for their next generation time-sharing systems, and the University of Michigan showed interest in Multics, corporate IBM woke up to the need for time-sharing and responded with the 360/67. IBM's concern over the "snowball effect" led them to announce plans to build a large-scale timesharing system, TSS/360, as described in an article by Judy O'Neill in the 1995 Annals of the History of Computing. So the 360/67 was the machine of choice for IBM's CP/CMS and TSS, as well as for the Michigan Terminal System, MTS, which was begun about the same time. The 360/67 was announced in August 1965, and 360/67 serial #2 was delivered to the University of Michigan in January 1967.

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CP-67 didn't use the segmentation features of the 360/67; In fact, segmentation was not a feature of the original Blaauw proposal, but was derived from a 1966 JACM paper by Arden, Galler, O'Brien, and Westervelt of Michigan. Both TSS and MTS did use segmentation, but not as pervasively as Multics did on the GE 645. The 645's descriptors contained the access permission bits, whereas access in the System/360 was controlled by a per-page storage key. The privileged instruction SSK (Set Storage Key), not available on all models, could set the key. User jobs each had their own key and could only write pages with their own key; the 360/67 added fetch protection. This was simpler than the 645 segmentation mechanism but precluded sharing of memory between jobs.

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