horalek@Alliant.COM (Jim Horalek) (07/06/90)
Now that the A3000 is out I'm feeling jealous. My lowly A2000 only has a 68000 and a 16bit bus. I pose the following, could the ZorroIII bus be supported on the A2000? Suppose some company such as GVP designed an accelerator board which provided a way to generate the necessary circuitry to make the ZorroII bus ZorroIII. What generates the Buss signals; one of the custom chips? Are the custom chips in the A3000 in anyway compatible with the A2000? Perhaps future A2000's should have a way to get to a ZorroIII buss. Anyone thought about replacing the A2000 motherboard with an A3000 motherboard? I know the A3000 motherboard has fewer slots but maybe this might be one upgrade path. Jim .nosig
daveh@cbmvax.commodore.com (Dave Haynie) (07/06/90)
In article <3976@alliant.Alliant.COM> horalek@Alliant.COM (Jim Horalek) writes: > Now that the A3000 is out I'm feeling jealous. My lowly A2000 >only has a 68000 and a 16bit bus. I pose the following, could >the ZorroIII bus be supported on the A2000? Suppose some company >such as GVP designed an accelerator board which provided a way to >generate the necessary circuitry to make the ZorroII bus ZorroIII. No. There are several problems with that idea. First of all, you can't easily get all the proper signals from the Coprocessor board down to the expansion backplane. And even if you could, the bus buffers of the Zorro II implementation in the 2000 are all wrong for Zorro III. Also, there are two obselete Zorro II signals (VPA*, VMA*) that would have to be cut away from the backplane to allow Zorro III to run on that backplane. And it's extremely unlikely that Zorro III speeds could be maintained on the A2000 backplane, which wasn't designed to go any faster than Zorro II. >What generates the Buss signals; one of the custom chips? Are the custom >chips in the A3000 in anyway compatible with the A2000? The A3000's Buster Chip. While they're both called "Buster", the A2000 version is an extremely simple chip, which replaces about four PAL devices. The A3000 Buster is a reasonably complicated gate array, made from several thousand gates. And of course, A2000 Buster listens to 68000 signals, A3000 Buster listens to 68030 signals, on the local bus interface side of things. >Anyone thought about replacing the A2000 motherboard with an A3000 >motherboard? I know the A3000 motherboard has fewer slots but maybe >this might be one upgrade path. It's technically possible, I suppose, to build an A3000 motherboard that would fit in an A2000 case (except for the CPU slot, which wouldn't have enough clearance under the A2000 power supply/disk drive frame). If Commodore Management decides they want to offer an A2000->A3000 upgrade program, it might be done this way. But that would be much more of a headache that simply taking in 2000s and money and giving back 3000s; any new circuit board must go through FCC certification. It's tough to get 3000-class frequencies clean in an A2000 case (witness the metal cage around the clock/CPU/FPU section on the A2630). On the other hand, the Zorro III specification does give the A2000 accelerator board designer the firmware standards necessary to go beyond the 8 Megabyte expansion limits of the Zorro II autoconfig specs. There's no reason you can't use Zorro III autoconfig without having a real Zorro III bus (this would have to be on the private 68030 bus, obviously it couldn't live on the Zorro II bus). > Jim > .nosig -- Dave Haynie Commodore-Amiga (Amiga 3000) "The Crew That Never Rests" {uunet|pyramid|rutgers}!cbmvax!daveh PLINK: hazy BIX: hazy "I have been given the freedom to do as I see fit" -REM