QBUS memories

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QBUS memory cards are available both from DEC, and from a large number of outside vendors who produced and sold QBUS memory cards.

Like the QBUS itself, QBUS memory cards can be divided into Q16, Q18 and Q22 memories. In addition, DEC later specified the PMI memory bus, an extension of the QBUS, and some memory cards have dual QBUS/PMI capability.

Using Q18 memory in Q22 machines

Note that although Q18 memory cards can be plugged into a Q22 machine (e.g. most 11/23's, and all 11/73's), and seem to work, they will not always function properly, and may cause subtle errors. (The sole exception to this rule is in machines with less than 256KB memory, total.)

This is because a Q18 memory configured for 000000 and up will also respond to bus cycles to 1000000 and up, 2000000 and up, etc.

Diagnosing DRAM memory failures

If a memory card has multiple banks of chips (e.g. a board built with 64Kx1 chips, so that one needs 16 chips to produce word-wide memory, but it has 32 chips), and one bank is picking or dropping bit(s), and the other(s) is/are not, that meant that data paths are all OK, and it is a simple matter of finding the bad memory chip(s).

This diagnostic heuristic is quite useful, since many PDP-11 semiconductor memory cards have (because of the physical size of DRAM chips, and QBUS cards) two or four banks of xxKx1 chips; so if a memory card has dropped/picked bits, look to see if all banks have the same fault. If 'no', it's pretty much guaranteed to be a memory chip, and it should be easy to find.

It is possible to repair memory cards with this failure mode without doing any hardware debugging at all; the symptoms, and the memory chip layout (given in the pages for many of the cards listed below), are all one needs.

DEC

Core memory

  • MMV11-A - 8-Kbyte unit (H653 and H223)

MOS memory

  • MSV11-B - 8-Kbyte (external refresh - M7944)
  • MSV11-C - (on-board refresh - M7955)
    • MSV11-CA - 8-Kbyte
    • MSV11-CB - 16-Kbyte
    • MSV11-CC - 24-Kbyte
    • MSV11-CD - 32-Kbyte
  • MSV11-D - (no parity - M8044)
    • MSV11-DA - 8-Kbyte
    • MSV11-DB - 16-Kbyte
    • MSV11-DC - 32-Kbyte
    • MSV11-DD - 64-Kbyte
  • MSV11-E - (parity - M8045)
    • MSV11-EA - 8-Kbyte
    • MSV11-EB - 16-Kbyte
    • MSV11-EC - 32-Kbyte
    • MSV11-ED - 64-Kbyte
  • MSV11-L - (M8059)
    • MSV11-LF - 128-Kbyte
    • MSV11-LK - 256-Kbyte
  • MSV11-M - (M7506)
    • MSV11-MA - 512-Kbyte
    • MSV11-MB - 1-Mbyte
  • MSV11-P - (M8067)
    • MSV11-PF - 128-Kbyte
    • MSV11-PK - 256-Kbyte
    • MSV11-PL - 512-Kbyte
  • MSV11-Q - (M7551)
    • MSV11-QA - 1-Mbyte
    • MSV11-QB - 2-Mbyte
    • MSV11-QC - 4-Mbyte
    • MSV11-SA - 2-Mbyte

PMI MOS memory

  • MSV11-J - (M8637)
    • MSV11-JB - 1-Mbyte
    • MSV11-JC - 2-Mbyte
    • MSV11-JD - 1-Mbyte
    • MSV11-JE - 2-Mbyte
  • MSV11-R - 1-Mbyte (ECC? - M7458)

Camintonn

Clearpoint

MOS memory

  • Q-RAM 11
    • Q-RAM 11-3 - 256-Kbyte, no parity
    • Q-RAM 11-3 - 256-Kbyte, parity
    • Q-RAM 11-1 - 512-Kbyte, no parity
    • Q-RAM 11 - 512-Kbyte, parity
  • Q-RAM 22B
    • Q-RAM 22(B)-3 - 512-Kbyte, no parity
    • Q-RAM 22(B)-3 - 512-Kbyte, parity
    • Q-RAM 22(B)-1 - 1-Mbyte, no parity
    • Q-RAM 22(B) - 1-Mbyte, parity
  • Q-RAM 88B
    • Q-RAM 88B-2 - 2-Mbyte
    • Q-RAM 88B - 4-Mbyte
  • DCME-Q2A
    • DCME-Q2A/256KB
    • DCME-Q2A/512KB
  • DCME-Q2B - 256-Kbyte / 512-Kbyte / 1-Mbyte / 2-Mbyte
    • DCME-Q2B/256KB
    • DCME-Q2B/512KB
    • DCME-Q2B/1MB
    • DCME-Q2B/2MB
  • DCME-Q4B
    • DCME-Q4B/512KB
    • DCME-Q4B/1MB
    • DCME-Q4B/2MB
    • DCME-Q4B/4MB

PMI MOS memory

  • QED1 (aka QED-F) - 2-Mbyte / 4-Mbyte
  • DCME-Q4E - 2-Mbyte / 4-Mbyte

Mostek

National Semiconductor

  • NS23C - 128-Kbyte / 256-KByte / 1-Mbyte, parity
  • NS23M - 256-Kbyte, parity
  • NS23S - 1-Mbyte, parity