Re: (Fwd) Re: 8032 crt vs. 3032 crt

From: A. Fachat <>
Date: Tue, 02 Jul 2013 08:05:12 +0200
Message-ID: <>
Am 2. Juli 2013 08:46:15 schrieb "MikeS" <>:
> It turns out that there is a routine in the graphic ROM that checks for 
> presence of the VIDEO ON signal on PB5 of the VIA that is not in the 
> business version; the problem was a broken trace from the PIA to the VIA.

Ah,  a remnant of the old PET 2001 "don't access the screen memory while 
displaying" code - that waited for retrace before printing to avoid snow on 
the screen.
This code is also the cause for the speed up poke that turned into a killer 

Didn't think it was still in the Basic4 editor.


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Received on 2013-07-02 07:00:03

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