Path: utzoo!utgpu!news-server.csri.toronto.edu!cs.utexas.edu!bcm!dimacs.rutgers.edu!rutgers!cbmvax!daveh From: daveh@cbmvax.commodore.com (Dave Haynie) Newsgroups: comp.unix.amiga Subject: Re: Adding Symmetric Multiprocessing to Amiga UNI Message-ID: <18407@cbmvax.commodore.com> Date: 31 Jan 91 23:39:18 GMT References: <994@swrinde.nde.swri.edu> > <20708@hydra.gatech.EDU> <1991Jan30.181208.1256@convex.com> <1991Jan31.154251.16107@nada.kth.se> Reply-To: daveh@cbmvax.commodore.com (Dave Haynie) Organization: Commodore, West Chester, PA Lines: 30 In article <1991Jan31.154251.16107@nada.kth.se> nv90-mho@dront.nada.kth.se (Magnus Holmberg) writes: > I'm not very good at hardware (esp. w/ the 3000). It seems > to me, though, that since the '040 wouldn't need to access > Chipmem much, in a setup like this, it might be possible to > run it on the same 'half-cycle' as the PAD. That way, the > CPU's wouldn't have to lock eachother out of the Fastmem-bus. The 32 bit bus is fully loaded by any '030 or '040 access; there's no spare time like there was on the 7.16MHz 68000 systems. Think of it this way -- the 68030's clock is 3.49 times that of the Amiga 68000 machines, and a 68030's fastest cycle is twice the speed, in clock cycles, of the 68000's fastest cycle. So, in order to run double cycles without wait states on an A3000, you would need a DRAM chip that cycles in roughly 20ns (that's a simplification, but you get the main idea). The 80ns parts in the A3000 are cycled at 200ns, 10 times too slow for such a trick. The best strategy for A3000 multiprocessing would be to have the 68040 off the main (shared) bus as often as possible, while the 68030 does whatever I/O operations it can handle. The large 68040 cache makes this a somewhat natural event anyway, but either private 68040 memory or a large external cache on an '040 coprocessor board would improve this considerably. > -MH -- Dave Haynie Commodore-Amiga (Amiga 3000) "The Crew That Never Rests" {uunet|pyramid|rutgers}!cbmvax!daveh PLINK: hazy BIX: hazy "What works for me might work for you" -Jimmy Buffett