Date:	Fri, 02 Mar 2001 12:54:26 +0200
From:	"Eli Zaretskii" <eliz AT is DOT elta DOT co DOT il>
Sender:	halo1 AT zahav DOT net DOT il
To:	damon AT redshift DOT com (Damon Casale)
Message-Id:	<2427-Fri02Mar2001125426+0200-eliz@is.elta.co.il>
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CC:	djgpp AT delorie DOT com
In-reply-to:	<3a9ebeb5.501470@news.redshift.com> (damon@redshift.com)
Subject:	Re: Using DMA for hard disk access?
References:	<3a9e955b DOT 2750392 AT news DOT redshift DOT com> <3405-Thu01Mar2001215625+0200-eliz AT is DOT elta DOT co DOT il> <3a9ebeb5 DOT 501470 AT news DOT redshift DOT com>
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> From: damon AT redshift DOT com (Damon Casale)
> Newsgroups: comp.os.msdos.djgpp
> Date: Thu, 01 Mar 2001 21:31:58 GMT
> >
> >Keep in mind that while DMA moves data from the disk to memory or
> >back, the system bus is not available.  Therefore, you will have bus
> >contention with any other device that goes through the bus.  VGA, for
> >example.
> 
> Would plain memory access (regardless of what it is) be going through
> the same bus?

It depends.  On most modern motherboards, the main memory doesn't go
through the system bus, AFAIK.

> >> I'm not entirely sure how to tell the hard drive what sectors I want
> >> to read or write, but I _think_ I know how to use the DMA I/O ports.
> >> Where would I look for more detailed info on this?
> >
> >In case you didn't see it, the DJGPP FAQ has something about using DMA
> >in section 18.13.
> 
> Yup, saw that already.  Thanks tho.  :-)

You should probably study some good book about DMA programming in
conjunction with PC and disk I/O.  The Undocumented PC is one of my
favorites.

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