MSV11-D/E MOS memory

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M8044 memory card

The MSV11-D (M8044) was a dual-height QBUS DRAM main memory card; the MSV11-E (M8045) is identical (apparently even using the same etch PCB), but adds byte parity. They were used in the LSI-11 PDP-11.

They held 64KB when fully populated with 16Kx1 DRAM chips. Initially they used 4Kx1 DRAMs, giving 16KB when fully populated; later/larger ones used 16Kx1 DRAMs. The memory is arranged as 2 banks, each 16 data bits (one PDP-11 word) wide, optionally with 2 additional bits for parity (1 per byte) in the MSV11-E. Half-populating them (i.e. 1 bank only) produced 8KB and 322KB sized versions (depending on DRAM type).

Four versions of the parity/non-parity types exist:

  • MSV11-DA, -EA - 8KB (4K DRAMs)
  • MSV11-DB, -EB - 16KB (4K DRAMs)
  • MSV11-DC, -EC - 32KB (16K DRAMs)
  • MSV11-DD, -ED - 64KB (16K DRAMs)

All are Q18 (hence, could not be used in Q22 systems, such as PDP-11/23's with more than 256KB of memory).

They had internal refresh.

A card tagged "M8044-EH" has been seen; this is probably the result of a production error. The MSV11-DC is tagged 'M8044-Cx' (where 'x' varies, depending on the source of the DRAM chips used), and the MSV11-DD is tagged 'M8044-Dx' (likewise). An "M8044-EH" thus implies it is an MSV11-DE - which does not exist.