QBUS memories

QBUS memory cards are available both from DEC, and from a large number of outside vendors who produced and sold QBUS main 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 PDP-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 01000000 and up, 02000000 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 with the need for a minimum of 16 chips to produce word-wide memory, if it has 32 chips, or two complete banks, for a total capacity of 256KB), 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 QBUS semiconductor memory cards have (because of the storage size of DRAM chips, and QBUS cards) two or more banks of nnKx1 chips; so if such 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 and fix.

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. See Repairing un-documented MOS memory boards for more.

DEC

Core memory

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

MOS memory

• MSV11-A - 2-Kbyte (static RAM)
• 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

PMI memories can generally also function as QBUS memories, except that they cannot be used in a Q/Q backplane.

• MSV11-J - (ECC, M8637)
  • MSV11-JB - 1-Mbyte (no QBUS)
  • MSV11-JC - 2-Mbyte (no QBUS)
  • MSV11-JD - 1-Mbyte
  • MSV11-JE - 2-Mbyte
• MSV11-R - 1-Mbyte (parity, M7458)

Camintonn

• CMV-250 - 256-Kbyte
• CMV-500 - 512-KByte
• CMV-254 - 1-MByte
• CMV-504 - 2-MByte
• CMV-1000 - 1-MByte
• CMV-4000 - 4-MByte

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

Monolithic Systems

• MSC 4601 - 64 Kbyte
• MSC 303-0289 - 256 Kbyte, parity
• MSC 303-0339 - 1 Mbyte, parity

Mostek

• MK8022 - 256-Kbyte

National Semiconductor

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

See also

• PMI memories
• Repairing un-documented MOS memory boards

External links

• Read/Write Memory Modules