The C.mmp Multiprocessor

Abstract : C.mmp1 is archtypical of a simple multiprocessor; it consists of a number of equal, asynchronous central processors that share a large primary memory. C.mmp differs from earlier multiprocessors such as the Burroughs D825, IBM 360/67, Honeywell 645 (Multics), etc. in two essential respects: (1) C.mmp is designed to have up to sixteen processors while other multiprocessors usually have no more than four processors. (2) C.mmp is constructed from minicomputer processors rather than the larger (32 to 48 bits/word) processors used in the other systems. In other words, the effective use of C.mmp requires that we find and exploit a much higher degree of parallelism than has been needed by earlier multiprocessors. In the past few years, the number of existing multiprocessors has increased significantly to include BBN's Pluribus, Stanford's S-1, and CMU's CM* systems. However, C.mmp still remains notable for its uniform structure and support of a general-purpose operating system. Moreover, performance studies of C.mmp provide calibration for similar data from these newer machines.