Clearpoint DCME/Q4E configuration
jnc at mercury.lcs.mit.edu
Tue Aug 18 09:20:15 CDT 2015
> From: Johnny Billquist
> DEC's memory boards never had any jumpers for PMI as such.
Yes, and if you plug one of their PMI memory boards into a Q/Q backplane, it
will emit magic smoke, too! :-)
I think that's why this thing has the jumpers - to allow it to be used in a
Q/Q backplane. It would, of course, only be normal (slower) QBUS memory, but
at least one could use it there.
However, I am unable to verify that hypothesis. (See below.)
I looked at the jumpers along the edge in the C/D finger region, and a lot
of them _do_ connect to pins used in the PMI bus. (Confusingly, a number
connect to _other_ pins - I can see I have some detective work in front
of me here!)
However, that made it likely that the one that had jumpers on all those pins
was configured for PMI use, so I rolled the dice, and tried plugging that
board into a Q22/CD backplane, along with a KDJ11-B, and after a short bout of
'tired memory' (see my previous post), it did come up as a 4MB PMI memory!
(Parity, though, not CRC - which might make sense, I guess - it has 148
memory chips on it, which is a multiple of 37, so 32 + byte parity, plus a
spare chip, I would guess?)
However, when I plugged the other one in - nada. No response at all; the boot
PROM bitched about 'no memory at 0'. So I'm not sure _what_ that
configuration is for.
So then I took a flier (although the cards use the identical PCB, they do
have a few minor differences in chip rev in a couple of the programmable
chips), and put the jumper config from the working PMI card onto the other
card, and it did 'sort of' come up as a PMI card.
The boot PROM was complaining about "Memory CSR Error" (I'll have to
investigate that further), _but_ the memory was shown (by the boot PROM 'map'
command) as PMI, and my own memory-test program showed it was all working OK.
Well, at least we have a jumper config that allows us to use these cards
as PMI memory!
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