>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. PLEASE TAKE NOTE: The contents of this email (including any attachments) may be privileged and confidential. Any unauthorised use of the contents is expressly prohibited. If you have received this email in error, please advise us immediately (you can contact us by telephone on +61 8 9441 2311 by reverse charge) and then permanently delete this email together with any attachments. We appreciate your co-operation. Whilst Orbital endeavours to take reasonable care to ensure that this email and any attachments are free from viruses or other defects, Orbital does not represent or warrant that such is explicitly the case (C) 2000: Orbital Engine Company (Australia) PTY LTD and its affiliates - This message was sent through the cbm-hackers mailing list. To unsubscribe: echo unsubscribe | mail firstname.lastname@example.org.
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