DEC Pro 350/380 Memory Cards - Interchangeability?

Mattis Lind mattislind at
Tue Aug 30 12:02:21 CDT 2016

> >> I misremembered the 350 (I don't have one): it can have memory in the
> I/O
> >> card cage, but it also has memory daughter cards, two of them, with 40
> pin
> >> connectors.
> >>
> > Many years ago I upgraded those daughter cards and changed them from
> using
> > 64kbit chips to 256 kbit chips. I don't remember the exact type which I
> > used. It was very successful. The system went from 512kbyte total to 1280
> > kbyte total. There were no stability issues what I remember so the
> refresh
> > seemed to have worked fine.
> You're talking about the Pro-380 daughtercard, right?  It has a jumper on
> the card to indicate to the software whether the card has 64k or 256k
> chips.  I don't see anything like that in the Pro-350 description.
No. Actually the 350. I still have the machine, though it hasn't been ran
for ages. I did this "upgrade" more than 25 years ago so the (my...) memory
is a bit fuzzy. But I think I remember that it was just a simple change of
chips. No extra wiring needed to handle the extra address bit, it was all

I just looked up the tech manual page 5-46: "The system can address up to
512kbytes per daughter board slot" so my memory wasn't that bad after all.

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