Date: 31 Aug 1999 15:14:01 -0400 From: Kevin Street <street@iname.com> To: Matthew Dillon <dillon@apollo.backplane.com> Cc: Soren Schmidt <sos@freebsd.dk>, current@FreeBSD.ORG Subject: Re: HEADS UP! ATA driver (atapi DMA).. Message-ID: <87906repae.fsf@mired.eh.local> In-Reply-To: Matthew Dillon's message of "Tue, 31 Aug 1999 10:59:35 -0700 (PDT)" References: <199908311213.OAA80049@freebsd.dk> <87btbnetgc.fsf@mired.eh.local> <199908311759.KAA25628@apollo.backplane.com>
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Matthew Dillon <dillon@apollo.backplane.com> writes: > :Two things I've noticed: > :1) my cdrom delivers about 2M/s which is the same as before DMA. Is > :the improvement only in cpu usage or should I be seeing a speed > :improvement too? > : > :speed tested with: > :dd if=/dev/racd0c of=/dev/null bs=64k count=320 > :(I get it to spin up with another dd before this test) > > Well 2MB/sec == 14x CDRom drive. Is it a 14x CDRom drive? CDRom > drives are typically limited to how quickly they can get data off > the platter. A faster bus transfer will not improve that. I should have mentioned that ... it's a 32x cdrom. dmesg says it claims to be able to do 5515 KB/sec. I've played around with using dd ... skip=n to reposition which part of the cd I'm reading and I've seen some much better speeds on the outer tracks (I think I now recall that cd's start numbering from the inside tracks, don't they?). So you're probably right that it's just the rotational speed that I was seeing. -- 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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