RE: Informations about JiffyDOS
Date: 2001-03-16 07:31:38

>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
>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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