From: "Tom St Denis" Newsgroups: comp.os.msdos.djgpp References: <3a9e955b DOT 2750392 AT news DOT redshift DOT com> Subject: Re: Using DMA for hard disk access? Lines: 23 X-Priority: 3 X-MSMail-Priority: Normal X-Newsreader: Microsoft Outlook Express 5.50.4522.1200 X-MimeOLE: Produced By Microsoft MimeOLE V5.50.4522.1200 Message-ID: Date: Thu, 01 Mar 2001 22:54:41 GMT NNTP-Posting-Host: 24.112.8.23 X-Complaints-To: abuse AT home DOT net X-Trace: news3.rdc1.on.home.com 983487281 24.112.8.23 (Thu, 01 Mar 2001 14:54:41 PST) NNTP-Posting-Date: Thu, 01 Mar 2001 14:54:41 PST Organization: Excite AT Home - The Leader in Broadband http://home.com/faster To: djgpp AT delorie DOT com DJ-Gateway: from newsgroup comp.os.msdos.djgpp Reply-To: djgpp AT delorie DOT com "Damon Casale" 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