*BSD News Article 20673


Return to BSD News archive

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