WTB: DEC Rainbow Expansion Memory

Warner Losh imp at bsdimp.com
Wed Apr 12 14:07:47 CDT 2017

On Wed, Apr 12, 2017 at 1:00 PM, Stephen Pereira
<spereira1952 at comcast.net> wrote:
> Thanks for your response.
> Just to be certain, I just tore it all down and reconfirmed, in case my
> memory was playing any tricks.
> I have a PC-100B with no expansion card.
> Thanks again for the advice.

Bummer. The cards come up from time to time in different places, but
there's none on ebay right now. Last summer there were like 5,
including one that had an 8087 coprocessor option...

> smp
> --
> Stephen M. Pereira
> Bedford, NH  03110
> On Apr 12, 2017, at 2:20 PM, Warner Losh <imp at bsdimp.com> wrote:
> On Wed, Apr 12, 2017 at 11:06 AM, Stephen Pereira via cctech
> <cctech at classiccmp.org> wrote:
> I’m looking for expansion memory for my DEC Rainbow.
> I currently have 128K RAM, and I’d like to have 256K RAM, so I can actually
> use the Lotus 1-2-3 that I recently purchased (without thinking).
> Any suggestions?
> So is this a 100A with a 64k expansion card? Or is it the 100B with no card?
> If you have the 100A and a 3-bank expansion card, you should be able
> to remove the 64k chips that are on there and replace them with 256k
> chips. You should be able to take it to 832k with 27 256kbit DRAM
> chips. 41256-120's in DIP 16 if I recall correctly. Need to set the
> DIP switches correctly. This is the easiest path forward, if you are
> lucky enough to have this configuration, since chips are easy to get,
> relatively speaking, and last time I priced them, they were ~0.70 each
> so this will set you back ~$20 from JAMECO. You'll want an anti-static
> setup to do this, since the BBSs were full of people that had done
> this w/o adequate setup blowing up their card / chips. IMHO, if you
> are going this route, it's not worth messing with 64k chips since the
> price difference is tiny and the win for 3 banks of 256k on the
> Rainbow is big.
> If you have a 100B with no expansion card, I can't help... The
> expansion card is the hard bit these days...
> Warner

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