MSV11-C MOS memory

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The MSV11-C (M7955) was a quad-height QBUS DRAM main memory card, introduced in 1975. They held 32KB when fully populated with 4Kx1 DRAM chips, in 4 8KB banks; several partially-populated variants were also available:

  • MSV11-CA - 8-Kbyte (M7955-YA)
  • MSV11-CB - 16-Kbyte (M7955-YB)
  • MSV11-CC - 24-Kbyte (M7955-YC)
  • MSV11-CD - 32-Kbyte (M7955-YD)

They are Q18 cards (hence, could not be used in Q22 systems, such as PDP-11/23's with more than 256KB of memory). Their starting address is configured by use of DIP switches.

They provided internal memory refresh, instead of requiring that it be performed externally, by the LSI-11 CPU, like the preceding MSV11-B MOS memory (although the MSV11-C can be configured with on-board jumpers to use external refresh).

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