Date: Tue, 31 Aug 1999 17:05:31 -0400 (EDT) From: Kevin Street <street@iname.com> To: Soren Schmidt <sos@freebsd.dk> Cc: current@FreeBSD.ORG Subject: Re: HEADS UP! ATA driver (atapi DMA).. Message-ID: <14284.17307.842265.468860@mired.eh.local> In-Reply-To: <199908311952.VAA80929@freebsd.dk> References: <87btbnetgc.fsf@mired.eh.local> <199908311952.VAA80929@freebsd.dk>
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Soren Schmidt writes: >Depends.. There are many factors involved here, using DMA only lowers >the CPU usage, and will enable faster transfers if the problem was >that the CPU was saturated with the PIO transfer. It gave about >double the transfer rate on my old P6 based maschine, because the >CPU drain was the limitting factor. Most modern CDROM are variable >speed, and you will see varying rates depending on the quality of >the media. dd'ing the whole cd and watching with iostat shows speeds from 2M increasing to 5.5M on the outside tracks with cpu staying at 98% to 100% idle on a PII 400. So DMA seems to be doing its stuff. I did try checking for correct data coming off the cd as well, and saw no problems. -- Kevin Street street@iname.com To Unsubscribe: send mail to majordomo@FreeBSD.org with "unsubscribe freebsd-current" in the body of the message
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