From:	"Tom St Denis" <tomstdenis AT yahoo DOT com>
Newsgroups:	comp.os.msdos.djgpp
References:	<3a9e955b DOT 2750392 AT news DOT redshift DOT com>
Subject:	Re: Using DMA for hard disk access?
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Date:	Thu, 01 Mar 2001 22:54:41 GMT
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"Damon Casale" <damon AT redshift DOT com> wrote in message
news:3a9e955b DOT 2750392 AT news DOT redshift DOT com...
> I'm trying to squeeze the last ounce of speed out of this compression
> program, and I'm wondering if switching to direct DMA calls, as
> opposed to using the INT13h or INT21h disk read-write calls, would
> help things much.  As far as programming in DJGPP goes, I know that it
> takes a lot of CPU cycles to switch from protected mode to real mode,
> and then back again, to make the interrupt calls.  Would I avoid that
> by doing DMA calls instead?
>
> Has anyone tried something like this?  If so, do you have any advice?
> 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?

Advice?  Um... oh I don't know... um DONT DO IT.

There is a reason int 21h exists... and it ain't to make things slow.

Tom

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