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Date: Tue, 21 Dec 2004 12:15:51 -0200
From: Jonatan Liljedahl <lijon AT kymatica DOT com>
To: djgpp AT delorie DOT com
Subject: Re: Problems with timer interrupt chaining and SmartDrv
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On 20 Dec 2004 20:49:09 GMT
Martin Str|mberg <ams AT speedy DOT ludd DOT ltu DOT se> wrote:

> Eli Zaretskii <eliz AT gnu DOT org> wrote:
> >> From: Martin Str|mberg <ams AT speedy DOT ludd DOT ltu DOT se>
> >> Date: 18 Dec 2004 11:09:24 GMT
> >> 
> >> Eli Zaretskii <eliz AT gnu DOT org> wrote:
> >> > It sounds like you are assuming that DMA is faster than PIO. 
> >That was> > so once, long ago, mainly with floppy drives, but is no
> >longer true> > since ATA interfaces conquered the PC land.  Nowadays,
> >PIO is faster> > than DMA, so AFAIK DMA is no longer used in disk
> >I/O.> 
> >> For DOS maybe, not for a multitasking system.
> 
> > Do you mean DMA is used on multitasking systems?  Or do you mean PIO
> > is only faster on DOS, not on multitasking systems?
> 
> > If the latter, please explain.
> 
> The former. And since DOS isn't multitasking it doesn't gain anything
> from the possiblity of the CPU doing something else but waiting for
> IO.

That not's true. Even if there aren't other programs running at the same
time, the program that IS running and doing I/O could very likely want
to do something while waiting for I/O! I know for sure that I'd like my
ongoing project (http://kymatica.com/kyce) to be able to keep on doing
stuff right after fwrite() is called, instead of the program being
blocked until I/O finishes.

/Jonatan    -=( http://kymatica.com )=-