MM11-K core memory

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G231 driver logic board

MM11-K core memory is a rare UNIBUS main memory system which is effectively an earlier, smaller version of the common MM11-L core memory.

Like the MM11-L, it consists of three cards, two of them the same as those of the MM11-L:

  • G110 - hex-format memory control logic and data channels
  • G231 - hex-format memory driver logic

The MM11-K also includes an 8 Kbyte H213 quad-format core memory stack card, instead of the 16 Kbyte H214 card of the MM11-L. It uses all the same custom backplanes as the MM11-L.

H213 core memoryboard

On the G110 module, two jumpers (W9 and W10) are set depending on whether it is being used with a 8 Kbyte or a 16 Kbyte core stack; for the MM11-K, W9 is installed, and W10 is removed. On the G231 module, two other jumpers (J3 and J4) are similarly set depending on the size; for the MM11-K, J3 is in, and J4 is out.

The effect of these jumpers is to send bus address line A13 to the 'device selector' circuitry, along with A14-A17, in the MM11-K (it goes to 'Decode X-switches', along with A10-A12, in the MM11-L).


MM11-K documentation does not appear to be extant; it is covered in the PDP-11/05 computer manual (below); and other MM11-L documentation is of course largely applicable.

See also

External links