The ACP multiprocessor system at Fermilab

Two versions of the ACP have been developed: one uses Motorola's 68020 32 bit microprocessor, the other runs with AT and T's 32100. Both include the corresponding floating point coprocessor chip. The first system when fully configured, uses 70 each of the two types of processors. A 53 processor system operates for several months with essentially no down time by computer operators in the Fermilab Computer Center, performing at nearly the capacity of 6 CDC Cyber 175 mainframe computers. The VME crates in which the processing ''nodes sit are connected via a high speed ''Branch Bus'' to one or more MicroVAX computers which act as hosts handling system resource management and all I/O in offline applications. An interface from Fastbus to the Branch Bus developed for online use which tests error free at 20 MBytes/sec for 48 hours ACP hardware modules are available commercially. A major package of software, including a simulator that runs on any VAX, has been developed. It allows easy migration of existing programs to this multiprocessor environment. This paper describes the ACP Multiprocessor System and early experience with it at Fermilab and elsewhere