DEC Pro 350/380 Memory Cards - Interchangeability?

Paul Koning paulkoning at
Tue Aug 30 11:18:45 CDT 2016

> On Aug 30, 2016, at 3:07 AM, Mattis Lind <mattislind at> wrote:
>> 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.

The Pro 380 schematics have a tantalizing hint that the motherboard memory could be populated with 256k memory chips.  At least that's what the "memory jumper configuration" note on sheet 4 of the PC380 system module schematics suggests.  Nothing else explains further, though.

The notes on the drawings also mention several different manufacturers, and the memory is described as "MOS memory ... 150 ns".

It turns out the schematics I have are the "PC380 system module" portion of what's already on Bitsavers in MP01922_PC380_EngrDrws_Jun84.pdf -- same revision.  The one extra bit of information is a hand-written note on the first sheet saying "these schematics match Rev E1 etch  03-MAY-84"


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