Recommendations for IMSAI-compatible RAM cards?

dwight elvey dkelvey at
Tue Jan 27 08:24:40 CST 2009

> Date: Mon, 26 Jan 2009 22:45:33 -0800
> From: derschjo at
> To:
> Subject: Recommendations for IMSAI-compatible RAM cards?
> Hey all --
> Acquired an IMSAI 8080 in half-assembled condition (but the price was
> right). I believe that (after doing some thorough cleaning, debugging,
> and replacing of old cabling) that I've got the front panel and CPU
> functioning correctly. However, the IMSAI came without any RAM cards so
> I'm unable to go any further at the moment.
> I have one S-100 RAM card but I have no documentation on it and it's
> missing a couple of ICs (and what they're supposed to be, I don't
> know). It's a PSS RAM65. My internet searches for info confirm that
> the card does indeed exist, but I can find no technical information.
> From my research, my understanding is that S-100 RAM cards are fickle
> and compatibility with front-panel machines can be an issue. Does
> anyone have any recommendations for what to look out for as I begin my
> search? Anyone have any decent RAM cards they'd be willing to part with?
> Thanks!
> Josh
Hi Josh
 If it is static RAM you should be able to make it work.
Don't even try with DRAM. You'd be luck to get them working
on a IMSAI. Most DRAM needs a running processor. If
you stop the processor you lose the data. Some do have
circuits to keep refresh going but these are only
the rarer early ones specifically designed for a
front panel machine.
 Have you done any tracing of the circuit. I had a card
once with a couple missing parts that I'd had sitting around
for a few years that I wanted to use. It was missing a
few parts as well. After tracing the circuit, I found
that the missing parts were for bank selection and were
not needed for normal use.
 Static RAMs have relatively simple circuits. Just
trace things out. ?The missing chips should be easy
to determine.

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