enabling DMA on hard drives

[Taavi Burns]

On Tue, 18 Jan 2005 18:47:32 -0500, Stewart C. Russell
<scruss-rieW9WUcm8FFJ04o6PK0Fg at public.gmane.org> wrote:
> The gain in speed might be quite small, I'd agree, but:
> 
> * it comes for free
> 
> * without DMA, watching DVDs on lower-end machines is an unpleasant
> exercise.

Yup.  DMA (Direct Memory Access) is the mechanism whereby the
CPU can tell the HD controller to "put this data here in memory," and
then ignore it until the transfer is complete.  Without using DMA, the CPU
must be involved in every step of the process.  This provides speed
gains when the system is CPU-bound, and in all cases greatly reduces
CPU load.

http://www.pcguide.com/ref/hdd/if/ide/modesDMA-c.html

-- 
taa
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