On Tue, 28 Mar 100 email@example.com wrote: > > Funny thing, and I don't know if anyone else has noticed this, is that > > when I used my CP/M cartridge, I would have to try about a billion times > > to get it to boot, but once it did boot, it would work for as long as I > > cared to use it for (which, to be honest, wasn't ever very long since it > > was so dang slow). Just an observation I thought I would throw in there. > > :) > > The times I used I never had problems booting except for the fact that the > resetbutton did "not" work. Possibly the reason why the cartridge sometimes only boots after several attempts is that the C64 has had time to warm up, hence changing its timing slightly. > > when the internal bus on the Z80 is in a "float" condition, the address > > multiplexorss on the CPM cart are exposed to a voltage that is neither a "1" > > nor a "0" > > This remark I do not understand. There are no multiplexers on the card, only > buffers. The Z80 itself is only tri-stated when the 6510 is active. It even is > not tristated when the VIC-chip is in command. In this case the buffers are > tri-stated. I think Bil means the address multiplexors inside the C64; the ones that connect to the DRAMs. If the CP/M cartridge somehow fiddles with the address lines at some cycle when it's not supposed to (eg. the DRAM refresh cycles) then this could certainly cause problems. Perhaps the Z80 doesn't get tristated off the bus *quick*enough*, and this leads to problems when the next cycle on the 6502 bus is a refresh cycle. Possibly. Richard - This message was sent through the cbm-hackers mailing list. To unsubscribe: echo unsubscribe | mail firstname.lastname@example.org.
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