C.mmp

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The C.mmp was an early MIMD multiprocessor system developed at Carnegie Mellon University by W.A.Wulf (1971).

Sixteen PDP-11 minicomputers were used as the processing elements (named Compute Modules in the system). Each CM had a local memory of 8K and a local disk subsystem.

Each of the Compute Modules shared these communication pathways:

An Interprocessor bus - used for distribution of system-wide clock, interrupt and process control messaging among the CMs
A 16x16 crossbar switch - used to connect the 16 CMs on one side and 16 banks of shared memory on the other.

Since the PDP-11 only had an address space of 16-bits, an additional address translation unit was added to expand the address space to 25 bits for the shared memory space.

The operating system was called HYDRA. It was an capability-based object-oriented operating system. System resources were represented as objects and protected through capabilities. Among the programming languages available on this system was a subset of ALGOL 68. This language was in fact more a superset than a subset, as the features supporting parallelism were vastly improved. It was operated from a PDP-10 multi-user system.