From: Nicolas Welte (welte_at_chemie.uni-konstanz.de)
Date: 2002-03-26 12:21:40
Richard Atkinson wrote:
> MOS
> 8563R6 4C
> 1285
>
> MOS
> 8563R7A
> 1885
>
> There are two of the latter chip. I've read hacker documentation advising
> the use of R8 or R9 chips, so does anyone know what the bugs are with
> these earlier chips?
I've been looking for a 8563R7 a long time myself, because this one is
actually documented in the C128 PRG to behave differently than R8/R9 in
bitmap modes, it needs a different horizontal scroll register setting (IIRC).
I'd be happy to get a working sample to play around with :-)
I never heard of the R6, but I think that the R7 was the first one that was
used in early production models. Early prototype machines are known to have
had the 'VIC tower', a PLL circuit that doubled the VIC dot clock and
supplied the VDC with it (the early revisions needed syncronous clocks on the
CPU and video interface). Rebuilding this circuit might be hard, but I once
wanted to do some timing measurements on the VDC and created my syncronous
clock by simply dividing the 16MHz VDC clock by two and feeding it as
dotclock into the VIC-II.
Nicolas
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