On 03/09/2014 07:18 PM, smf wrote: >> Yes, unfortunatly. Would have been nicer to keep the static design >> when it comes to address lines and run everything through the >> multiplexers as well (as was done with TED later). But I think the >> 6567 doesn't have enough Pins to do that since you'd still need _RAS >> and _CAS. > > They wouldn't have needed RAS_ or CAS if they used the same multiplexer > as the CPU. Well, someone has to generate the address strobes for the DRAMs. You can do that in TTL as well, but it takes a number of gates to do it properly. The way it was done in the C64 is a bit of a hack, but it saved on expensive logic and pins on VIC at the same time. The multiplexer for the CPU are controlled by _CAS from VIC by the way. VIC does the DRAM timing for itself AND the CPU, generating 2 complete RAS/CAS cycles for every single PHI0 cycle. > It's possible it wouldn't have met some dram timing doing it that way. Well, TED does it and it works. Gerrit Message was sent through the cbm-hackers mailing listReceived on 2014-03-09 19:01:07
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