RE: Informations about JiffyDOS

From: Professor Dredd (
Date: 2001-03-16 15:07:16

I'd recommend contacting CMD directly and ask
permission to implement a JiffyDOS COMPATIBLE protocol
in your device. Specifically state that you are coding
your own KERNAL so they know you're NOT pirating their

--- wrote:
> >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 ;)
> I agree that it really wouldnot be all that
> difficult to translate between
> the two kernals and create a patched VIC20 kernal.
> The CIA timers are used
> for measuring delays between signals etc, but as
> this is all free-running
> clock stuff, the 6522's counters should handle it
> also... most other stuff
> is done as delay loops, and functions such as
> switching off sprites etc
> could be removed to clean up the code....
> The main issue I feel is copyright vs patent.  CMD
> has the copyright to the
> JD code, but has the transmission protocol been
> patented. If it hasn't then
> provided one simply didn't copy the C64 or C128
> code, a VIC20 version of JD
> could be created.... Unfortunately I don't know the
> answer to the patent
> /copyright question.... it would be good to know as
> I intend 64HDD to
> eventually offer JD protocol support.
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