RE: cbm 8032 motherboard + 4164

From: Baltissen, GJPAA (Ruud) <>
Date: Wed, 12 Oct 2016 06:21:00 +0000
Message-ID: <>
Hallo allemaal,

>> 41256 need 8Bit refresh...

Oops, Gerrit and Marko are right: 8 bits refresh indeed. Where I got wrong is that one would expect that the 256 would need 9 cycles but only needs 8 as well. And that's why the 256 should be able to replace a 4164 (after tying A8 to Vcc or GND). But the 414256 (256K*4) does need 9 refresh cycles

But that rises a question for Didier: did you replace all 4116s with a 4164? It is now obvious to me you have other wise you would have ended up with 16 KB of RAM. 

And now I also realized again why I haven't done the 256 KB hack years ago: it involves quite a bit of work:
- isolating the lines leading to A7 and A8 by cutting various power lines
- removing capacitors on the isolated part
- creating an extra refresh bit
The actual work wasn't the problem but mutilating a working board was. But nowadays I have some boards laying around that I received broken and managed to repair. So it is still possible....

Met vriendelijke groet / With kind regards,
Ruud Baltissen

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Received on 2016-10-12 07:00:02

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