From: ddd42961@uxa.cso.uiuc.edu (Daniel D Deavours) Subject: Re: Abysmal disk performance Date: Thu, 14 May 1992 21:52:50 GMT
>> The string instructions (ie portread / portwrite in hd.c) are abysmally slow
>> in comparison to DMA. The same can be said for strcpy(). We should
>As I remember the 8237 DMA clicks along at 3 Mhz on the original AT
>coupled with
>10-15 wait states. I don't know how many wait states used on 386 boxes today
>but I believe the DMA is still at 3Mhz. Starting with the 286 and beyond
>doing a REP INS would transfer at bus speed.
Never programmed a DMA before, but if I'm correct, the advantage may not be
so much speed in data transfer, but the ability to do disk i/o in the back-
ground. It's annoying, especially on my slow hd/controller for everything to
wait until the hard drive is done (especially when syncing.)
I'm very much for that happening.
Dan Deavours