Performance of the GE-645 associative memory while Multics is in operation

ABSTRACT

The Multiplexed Information and Computing Service (Multics) of Project MAC at M.I.T. runs on a General Electric 645 computer system. The processors of this hardware system contain logic for both paging and segmentation of addressable memory. They directly accept two-part addresses of the form (segment number, word number) which they translate into absolute memory addresses through a series of indexed table lookups. To speed this address translation each processor contains a small, fast associative memory which remembers the most recently used address translation table entries. This paper reports the results of performance measurements on this associative memory. The measurements were made by attaching an electronic counter directly to a processor while Multics was in operation, and were taken for several associative memory sizes. The measurements show that for the observed load 16 associative registers are enough.

REFERENCES

• 1: Corbat@, F.J., et al, "A New Remote-Accessed Man-Machine System", AFIPS Conference Proceedings 27 (1965 FJCC), Spartan Books, Washington, D.C., 1965, pp. 185-247.
• 2: Peter J. Denning, Virtual Memory, ACM Computing Surveys (CSUR), v.2 n.3, p.153-189, Sept. 1970 [doi>10.1145/356571.356573]
• 3: GE-645 Processor Reference Manual, Cambridge Information Systems Laboratory, General Electric Company, August, 1970.
• 4: A. Bensoussan , C. T. Clingen , R. C. Daley, The multics virtual memory, Proceedings of the second symposium on Operating systems principles, October 20-22, 1969, Princeton, New Jersey [doi>10.1145/961053.961069]
• 5: Shemer, J.E., and G.A. Shippey, "Statistical Analysis of Paged and Segmented Computer Systems", IEEE Transactions on Electronic Computers EC-15, 6 (December, 1966), pp. 855-863.
• 6: Franklin D. Schulman, Hardware measurement device for IBM system/360 time sharing evaluation, Proceedings of the 1967 22nd national conference, p.103-109, January 1967, Washington, D.C., United States [doi>10.1145/800196.805980]

INDEX TERMS

Primary Classification:
  D. Software
  D.4 OPERATING SYSTEMS
      D.4.8 Performance
          Subjects: Measurements

Additional Classification:
  B. Hardware
  B.3 MEMORY STRUCTURES
      B.3.2 Design Styles
          Subjects: Associative memories

  H. Information Systems
  H.1 MODELS AND PRINCIPLES
      H.1.2 User/Machine Systems

General Terms:
Design, Human Factors, Management, Measurement