IBM M44/44X

The IBM M44/44X was an experimental computer system from the mid-1960s, designed and operated at IBM's Thomas J. Watson Research Center at Yorktown Heights, New York. It was based on a modified IBM 7044 (the 'M44'), and simulated multiple 7044 virtual machines (the '44X'), using both hardware and software. Key team members were Dave Sayre and Rob Nelson. This was a groundbreaking machine, used to explore paging, the virtual machine concept, and computer performance measurement. It was purely a research system, and was cited in 1981 by Peter Denning as an outstanding example of experimental computer science.[1]

History of IBM mainframe operating systems
Early mainframe computer OSes
Miscellaneous S/360 line OSes
DOS/360 and successors (1966)
OS/360 and successors (1966)
VM line
TPF line
UNIX and Unix-like

The term virtual machine probably originated with the M44/44X project, from which it was later appropriated by the CP-40 team to replace their earlier term pseudo machine.

Unlike CP-40 and later CP/CMS control programs, M44/44X did not implement a complete simulation of the underlying hardware (i.e. full virtualization). CP-40 project leader Robert Creasy observed:

The M44/44X "was about as much of a virtual machine system as CTSS – which is to say that it was close enough to a virtual machine system to show that 'close enough' did not count. I never heard a more eloquent argument for virtual machines than from Dave Sayre."[2]

M44/44X "implanted the idea that the virtual machine concept is not necessarily less efficient than more conventional approaches" – a core assumption in the CP/CMS architecture, and one that ultimately proved very successful.[3]

References
  • L. Belady, "A study of replacement algorithms for virtual storage computers," IBM Systems Journal Vol. 5, No. 2 (1966), pp. 78-101
  • L. Belady and C. J. Kuehner, "Dynamic space sharing in computer systems," Communications of ACM Vol. 12 No. 5 (May 1969), pp. 282-288
  • L. Belady, R. A. Nelson, and G. S. Shedler, "An anomaly in the space-time characteristics of certain programs running in paging machines," Communications of the ACM Vol. 12, No. 6 (June 1969), pp. 349-353
  • R. W. O'Neill. Experience using a time sharing multiprogramming system with dynamic address relocation hardware. Proc. AFIPS Computer Conference 30 (Spring Joint Computer Conference, 1967). pp. 611–621. doi:10.1145/1465482.1465581.
    – describes the M44/44X, reports performance measurements related to memory and paging, and discusses performance impact of multiprogramming and time-sharing
  • R. A. Nelson, "Mapping Devices and the M44 Data Processing System," Research Report RC 1303, IBM Thomas J. Watson Research Center (1964)
    – about the M44/44X
  • D. Sayre, On Virtual Systems, IBM Thomas J. Watson Research Center (April 15, 1966)
    – an early virtual machine paper describing multiprogramming with the M44/44X.
  • Melinda Varian, VM and the VM community, past present, and future, SHARE 89 Sessions 9059-9061, 1997
    – the outstanding source for CP/CMS and VM history

Citations

  1. Denning, op. cit.
  2. Creasy, op. cit. – relationship between M44/44X and CP-40
  3. L. Talkington, "A Good Idea and Still Growing", White Plains Development Center Newsletter, Vol. 2, No. 3 (March 1969) [quoted in Varian, op. cit., p. 10, Note 26]
CP/CMS family relationships
→ derivation     >> strong influence     > some influence/precedence
 CTSS 
> IBM M44/44X
>> CP-40/CMS → CP[-67]/CMS  → VM/370 → VM/SE versions → VM/SP versions → VM/XA versions → VM/ESA → z/VM
→ VP/CSS
> TSS/360
> TSO for MVT → for OS/VS2 → for MVS → ... → for z/OS
>> MULTICS and most other time-sharing platforms
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