Date: Tue, 31 Aug 1999 10:59:35 -0700 (PDT) From: Matthew Dillon <dillon@apollo.backplane.com> To: Kevin Street <street@iname.com> Cc: Soren Schmidt <sos@freebsd.dk>, current@FreeBSD.ORG Subject: Re: HEADS UP! ATA driver (atapi DMA).. Message-ID: <199908311759.KAA25628@apollo.backplane.com> References: <199908311213.OAA80049@freebsd.dk> <87btbnetgc.fsf@mired.eh.local>
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: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.
:2) I can crash my system (sometimes a panic, sometimes a freeze) with:
:dd if=/dev/racd0c of=/dev/null bs=1m count=1
:
:I could do bs=1m before the DMA code went in.
:
:If the system freezes I see:
:atapi_error: READ_BIG - timeout error = 00
:<long pause>
:the dd puts out a message about transferring 0 records
(This is a different problem, one I can't address. Presumably someone
else can).
-Matt
Matthew Dillon
<dillon@backplane.com>
:Kevin Street
:street@iname.com
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