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Newsgroups: comp.os.386bsd.questions Path: sserve!newshost.anu.edu.au!munnari.oz.au!news.Hawaii.Edu!ames!elroy.jpl.nasa.gov!swrinde!cs.utexas.edu!uunet!noc.near.net!Lotus.com!Temp.lotus.com!temp!jkh From: jkh@thrush.lotus.com (Jordan K Hubbard - he's back again) Subject: Re: FreeBSD: Does it solve the 16M problem In-Reply-To: nbladt@autelca.ascom.ch's message of Thu, 9 Sep 1993 06:41:33 GMT Message-ID: <JKH.93Sep9162315@thrush.lotus.com> Sender: news@lotus.com Nntp-Posting-Host: 130.103.186.134 Organization: Lotus Ireland References: <g89r4222.747163756@kudu> <26itba$eaj@pdq.coe.montana.edu> <CD2qLA.vq@autelca.ascom.ch> Distribution: world Date: Thu, 9 Sep 1993 15:23:15 GMT Lines: 27 >So, is it OK to use addresses higher than 16MB for DMA on an EISA system ? Just so long as you're using a DMA using disk controller in EISA mode, rather than ISA mode, yes - it will. For those who may find such a distinction confusing, let me explain: You can use an ISA controller (such as an Adaptec 1542) in an EISA machine, but as it will still think it's in an ISA box and refuse to use the extra address lines, this is no different than having an ISA machine as far as >16MB is concerned. You can use an EISA controller in "ISA mode", meaning it uses the older protocols for compatability reasons (examples being Adaptec 1742 in "standard" mode, DTC 3290 in "Adaptec" mode, etc) and again, does not use the extra address lines. The only way to get full EISA, 32MB-of-memory-and-everything, mode is to use an EISA controller in full EISA mode (for Adaptec 1742, this is "enhanced" mode, for DTC 3290 it's "DTC" mode). FreeBSD (and NetBSD) currently support the Adaptec 1742 in enhanced mode. I don't think there is any other combination that will get you more than 16MB in an EISA machine at the moment. Jordan