Re: 6545 40/80 col register values

From: MikeS <>
Date: Wed, 25 Apr 2012 02:28:52 -0400
Message-ID: <81E8BB456B284A3999CF262F56499CAA@vl420mt>
----- Original Message ----- 
From: "Baltissen, GJPAA (Ruud)" <>
To: <>
Sent: Wednesday, April 25, 2012 1:56 AM
Subject: RE: 6545 40/80 col register values

> For those not familiar with the CBM hardware:
> - an 80-cols machine has 2 KB of RAM instead of 1 KB for the 40-cols one, 
> not a real problem
> - this RAM is wired in a different way for each machine. And that is a 
> problem!
> I used to have a board equiped with some added 74157 2-to-1 demultiplexers 
> replacing those wires plus a small board with extra ROMs. By flipping a 
> switch one could have either 40-cols or 80-cols mode after a reset.

As a matter of fact Steve and I were just discussing that a few days ago; as
you say, the hardware to switch RAM & ROM etc. is pretty straightforward,
but we were speculating if it were feasible to switch modes (preferably in
software with a poke or printing a CHR$(x) ) *without* resetting the


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Received on 2012-04-25 07:00:21

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