Relay-Version: version B 2.10 5/3/83; site utzoo.UUCP Path: utzoo!utgpu!water!watmath!clyde!cbosgd!ihnp4!alberta!edson!tic!ruiu From: ruiu@tic.UUCP Newsgroups: comp.dcom.lans,comp.sys.ibm.pc Subject: Re: IBM PC/AT DMA loses (was Re: PC LAN Comparison) Message-ID: <162@tic.UUCP> Date: Wed, 25-Nov-87 00:07:42 EST Article-I.D.: tic.162 Posted: Wed Nov 25 00:07:42 1987 Date-Received: Sun, 29-Nov-87 02:02:30 EST References: <2070@killer.UUCP> <1020@kodak.UUCP> <155@tic.UUCP> <261@kaos.UUCP> <1560@cup.portal.com> Organization: U of A, E.E., Edmonton,Canada Lines: 27 Xref: utgpu comp.dcom.lans:865 comp.sys.ibm.pc:8999 Summary: All this seems to make the dual ported approach more sensible. [The discussion is about why DMA would be slower on an AT than polled I/O] In light of the facts pointed out by everyone, a poor implementation of DMA seems to be available on the AT. A certain traditionalist streak in me refuses to accept a tight loop as the highest performance data transfers. So if DMA is no good, then what is the high performance approach needed to 'squeeze' every ounce of performance out of an AT ? An aquaintance who is designing a major PC based hardware project has chosen to use double-ported memory. Truett Smith has already suggested this as the solution. So, in light of the dropping cost of such devices, they are the preferred way to go. Right ? Does anyone care to comment? Does anyone know of any products that use this approach to data transfers ? (What did I start with that innocuous first posting ??!!? :-) -- Dragos Ruiu Disclaimer: My opinons are my employer's, I'm unemployed! UUCP:{ubc-vision,mnetor,vax135,ihnp4}!alberta!edson!tic!dragos!work (403) 432-0090 #1705, 8515 112th Street, Edmonton, Alta. Canada T6G 1K7 Never play leapfrog with Unicorns...