pdp11/84 PMI memory: What is the problem with Q bus?

Noel Chiappa jnc at mercury.lcs.mit.edu
Wed Apr 22 10:34:33 CDT 2020

    > From: Chris Zach

    > in place of my quad height 11/73 CPU with 2mb memory.

Sorry, which exact quad-height CPU card? 

{As someone else has previously pointed out, the /73 and the /83 are basially
the same machine (roughly the same CPU board - KDJ11-B, perhaps with different
clock crystals), just with different memories - QBUS in the /73, PMI in the
/83.  The /84 is an /83 with i) a different backplane and ii) a KTJ11-B UNIBUS

    > On the positive side it's chock full of 256k chips, which I could pull
    > off and put on the EA board to bring it up to 2mb memory. I have air
    > heat tools and a pre-heater so getting the chips off should be pretty
    > basic.

I would advise against that. 256K chips are readily available on eBait, and
for not much money. Pulling them may damage them, and may well also do some
damage to the memory card, in addition to making it useless.

    > Getting them on the new board though could be a pain since all the
    > holes are soldered over....

A vacuum desoldering station will easily open them. Used Hakkos can be found
on eBait for not too much money.


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