Path: utzoo!utgpu!news-server.csri.toronto.edu!cs.utexas.edu!wuarchive!zaphod.mps.ohio-state.edu!usc!snorkelwacker!apple!olivea!oliveb!amiga!cbmvax!daveh From: daveh@cbmvax.commodore.com (Dave Haynie) Newsgroups: comp.sys.amiga.hardware Subject: Re: 80386 bridgeboard Message-ID: <13851@cbmvax.commodore.com> Date: 16 Aug 90 22:27:28 GMT References: Reply-To: daveh@cbmvax (Dave Haynie) Distribution: comp Organization: Commodore, West Chester, PA Lines: 31 In article Chuck.Phillips@FtCollins.NCR.COM (Chuck.Phillips) writes: >Make me the fourth or fifth who would consider the purchase _provided_ it >is a real 80386, not an 80386sx (and if the price is right). There is a >reason people buy 32 bit RAM for their MC68020 and MC68030 Amigas. This >reason (throughput) also applies to the 80386. (The SX might be a good low >cost option for the 68000 based Amigas, however.) There are several other issues when you're talking about an 80386. 68000 code is 32 bit code, even when run on a 68008. So a 32 bit CPU like a 68030 can take full advantage of a 32 bit bus. On the other hand, an 80386 running code for an 8088, 8086, or 80286 will only be running 16 bit code and 16 bit data. So the full 32 bit bus isn't much of an advantage until you're dealing with real life 80386 programs. I suspect the 80486 may partially solve this problem by doing 32 bit burst prefetches to cache even for the 16 bit instructions. In any case, the main speed advantage of the '386 over the '286 for 99% of the stuff run on MS-DOS machines has been the faster clock -- the fastest '286 is the 16MHz part made by AMD, the '386s are available at 33MHz (from Intel of course). At the same clock speed, '286s often run the same 8086 code faster than '386s. Now if you're planning to use a real [32 bit] OS, like perhaps UNIX, on your Bridge Card, the difference between a 16 and 32 bit bus could be as much as 2x, though likely somewhat less (eg, even on a 32 bit machine, not all operations are 32 bits wide). >Chuck Phillips MS440 -- Dave Haynie Commodore-Amiga (Amiga 3000) "The Crew That Never Rests" {uunet|pyramid|rutgers}!cbmvax!daveh PLINK: hazy BIX: hazy Get that coffee outta my face, put a Margarita in its place!