MD10 core memory

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The MD10 was a core main memory system for the early PDP-10s, principally the KA10. An MD10 could contain two to four 32KW memory modules, for a maximum of 128KW; access time is 0.8 μseconds, and the cycle time is a maximum of 1.8 μseconds. It connected to the so-called external memory bus of the 18-bit address form; parity is provided to protect the memory contents.

It was a multi-port memory, with 4 ports per memory system: the CPU uses one port (in a multi-processor system, one per CPU); the others are used by channels (such as a DF10) for mass storage such as disks.

Each port on each module could be independently set for its address, and for two-way interleaving (using address bits 20 and 35); each port can also be four-way interleaved (on all modules at once), using address bits 19 and 34.

Internal interleaving (among modules in a single MD10) is not productive; the whole MD10 is tied up whenever any module is active.

Each port and each module can independently be completely disabled (i.e. all modules from a single port, or all ports from a single module; but not a single module from a single port).