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Path: euryale.cc.adfa.oz.au!newshost.carno.net.au!harbinger.cc.monash.edu.au!news.cs.su.oz.au!metro!metro!munnari.OZ.AU!news.ecn.uoknor.edu!feed1.news.erols.com!howland.erols.net!news.mathworks.com!EU.net!usenet2.news.uk.psi.net!uknet!usenet1.news.uk.psi.net!uknet!dispatch.news.demon.net!demon!arg1.demon.co.uk From: Andrew Gordon <andrew.gordon@net-tel.co.uk> Newsgroups: comp.unix.bsd.freebsd.misc Subject: Re: DMA Date: Thu, 21 Nov 1996 19:26:35 +0000 Lines: 13 Message-ID: <3294ACEB.41C67EA6@net-tel.co.uk> References: <328C8861.48A3@mercurio.uc.pt> <56mjnr$b4a@uriah.heep.sax.de> <329083AC.7048@mercurio.uc.pt> <56vtd6$1mo@anorak.coverform.lan> NNTP-Posting-Host: arg1.demon.co.uk X-NNTP-Posting-Host: arg1.demon.co.uk X-Mailer: Mozilla 3.01Gold (X11; I; FreeBSD 2.1.5-RELEASE i386) MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Transfer-Encoding: 7bit Brian Somers wrote: > btw, does > anyone know how many usable address lines a PCI bus has ? 32 (or 64 or 30, depending on your point of view). PCI has multiplexed address/data - on the first cycle, an address is transferred, followed by an arbitrary number of sequential data words. Standard PCI is 32-bit, but there is also a 64-bit version. For memory accesses, the address must be word-aligned, so in this case you could say it's only 30 bits (separate byte enables allow you to do byte-wide memory cycles, but you do it by addressing a whole 32-bit word and selecting the desired byte out of it.