Re: Dating a C-64 board

From: Andre Fachat (
Date: 1999-04-18 23:34:20

Ethan Dicks wrote:
> > > 1.0Mhz, IIRC.
> > 
> > The NTSC VIC-20 runs at the same speed at the NTSC C64...
> I don't think that's correct.  In my original 1541 manual, it mentions the
> U+ and U- commands to change the IEEE speed to match VIC-20 or C-64 speeds.

The U+/U- has nothing to do with the actual clock frequency, but
with the handling of the bad lines in the C64, that the 
VIC20 does not have. Any appearance of a bad line during an IEC
transfer must be taken care of, and that's why the VC1541 has
to be made slower for the C64.


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Andre Fachat, Institute of physics, Technische Universität Chemnitz, FRG
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