From: MagerValp (MagerValp_at_cling.gu.se)
Date: 2008-09-17 17:05:46
>>>>> "RB" == <email@example.com> writes: RB> - are there 6809 experts amongst us? I've done a little bit of 6809 asm (Vectrex, home-made dual 6809 project that was never finished), but I'm hardly an expert. If you know 6502, it takes less than a day to learn 6809. Daniel beat me to it, and as he said you need a 6809E, which supports external clock circuitry and can tristate the bus. RB> - beside the well known "because it can be done", is there another RB> reason we benefit from a 6809 in a C64? Do you need another reason? :) I always thought the 6809 is ideal for writing your own operating system, something I played around with 10+ years ago. If you want to go really bonkers, mount two 6809Es with a little bus arbitration logic in the socket to play with SMP. The 6809 doesn't hit the bus on every clock cycle like the 6502 does, so letting two take turns should work pretty well. I have no idea where my notes are, but ISTR RMW instructions use the bus for three consecutive cycles, and can be used to implement semaphores. -- ___ . . . . . + . . o _|___|_ + . + . + . Per Olofsson, arkadspelare o-o . . . o + MagerValp@cling.gu.se - + + . http://www.cling.gu.se/~cl3polof/ Message was sent through the cbm-hackers mailing list
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