Asymmetric Multiprocessing - IBM System/360 Models 65MP and 67-2

IBM System/360 Models 65MP and 67-2

IBM offered dual-processor computer systems based on its System/360 model 65 and the closely related model 67. The operating systems which ran on these machines were OS/360 M65MP and TSS/360. There was also software developed at universities which used both CPUs, notably MTS. Both processors had access to the data channels, and so could initiate I/O.

M65MP was closer to SMP than MCP for the B5000 or TOPS-10 for the DECsystem-1055, since the operating system kernel ran on both processors (though with a “big lock” around the I/O handler) and peripherals could generally be attached to either processor.

The MTS supervisor (UMMPS) ran on either or both CPUs of the IBM System/360 model 67-2. Supervisor locks were small and were used to protect individual common data structures that might be accessed simultaneously from either CPU. As with M65MP, Individual tasks (jobs, processes) would only execute on one processor at a time.