RE: Informations about JiffyDOS
Date: 2001-03-16 01:59:32

On Fri, 16 Mar 2001, MagerValp wrote:

> >>>>> "BZ" == Bo Zimmerman <> writes:
> BZ> Hmmm... doesn't the VIC-20 use a different IO chip (the 6522) than
> BZ> the C64 (6526)? How would this effect even the attempt to code a
> BZ> jiffydos kernal for the VIC?
> Well, I'm guessing that you could use a lot of the code from the 1541
> JD rom, but I doubt it'd be a weekend hack...

The C64's original kernal rom isnt that different from the vic20's kernal
rom.  It's simply shifted up 3 bytes because the basic rom needs a jmp $e000
to span the gap the I/O space causes between the two roms.  In the vic20,
these roms are adjacent in the memory map, and the jmp is unneeded.  You
most likely could, with careful examination, modify all I/O accesses to the
CIAs to point to the VIAs in the vic20, and shift the routines down 3 bytes,
then reassemble them.  If someone knows if JD uses features not present in
the 6522, I'd love to know ;)


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