WTB: DEC Rainbow Expansion Memory

Stephen Pereira spereira1952 at comcast.net
Wed Apr 12 14:00:26 CDT 2017

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.

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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