finkel@TAURUS.BITNET (04/07/89)
Hello everyone! I remember reading that the B2000 CPU slot is actually the same as the A500 expansion slot. Is it also the opposite? Is it possible to build a simple adapter that will let me use the A2620 with my A500? thanks, Udi finkel@taurus.BITNET
daveh@cbmvax.UUCP (Dave Haynie) (04/08/89)
in article <8904062025.AA07916@MATH.Tau.Ac.IL>, finkel@TAURUS.BITNET says: > I remember reading that the B2000 CPU slot is actually the same as the > A500 expansion slot. Is it also the opposite? Actually, the B2000 CPU slot is a superset of the A500 expansion slot, for the most part. There are definitely some things on the CPU slot that aren't available on the A500 expansion slot. The main additions are the three signals that make up the "Coprocessor interface", which is a bit of magic that lets a coprocessor card like the A2620 turn off the 68000 and at the same time get DMA requests from the expansion bus routed to it instead of to the 68000. > Is it possible to build a simple adapter that will let me use the A2620 > with my A500? It's possible, but a little bit of a kludge. The main concern is that the A500 expansion port doesn't have the 7.16 mHz system clock needed by the A2620. On an A1000 you could change two jumpers on the A2620 to let you use the C1 and C3 clocks instead, but unfortunately, these clocks aren't accurate enough on A500s to let you make a sufficient 7.16 mHz clock replacement. So you'd need to run a wire from inside the A500 to the board you build to accept the A2620. Next thing is what to do about the coprocessor interface. The easiest thing to do would be to remove the 68000, as done on the German version of the A2000. I believe it's possible to actually keep the 68000 in place and switch between it and the 68020, but it would take more logic that is needed simply to get the A2620 running with an A500. > finkel@taurus.BITNET -- Dave Haynie "The 32 Bit Guy" Commodore-Amiga "The Crew That Never Rests" {uunet|pyramid|rutgers}!cbmvax!daveh PLINK: D-DAVE H BIX: hazy Amiga -- It's not just a job, it's an obsession