On Monday September 30 2002 11:19 am, s wrote:
> On Monday 30 September 2002 09:55 am, et wrote:
> > On Monday 30 September 2002 10:26 am, you wrote:
> > > Tom,
> > >
> > > Your comments bring up a question...
> > >
> > > In Windows, enabling DMA for CD-ROMs (and it variants) is
> > > considered a 'no-no' and will cause problems most every time.
> >
> > really? my DVD wants DMA to work at all in winders
> > cause it is much faaaaaaaaaaaaaster
>
> I've tried to check mine a couple of times (when this topic comes up)
> and hdparm always says it's not support on my drives if I use
> /dev/scdX and if I use /dev/hdx I get input output errors. Could
> this be because I have them set up under scsi emulation? Any other
> thoughts?
> thanks,
> -s
I believe so, but you should still be able to enable dma.
(my ide burner which has scsi emulation and is dev/scd0 or hdd, dma
enabled)
tom# hdparm -t /dev/scd0
/dev/scd0 not supported by hdparm
tom# hdparm -t /dev/hdd
tom# hdparm -t /dev/hdd
/dev/hdd:
Timing buffered disk reads: read() hit EOF - device too small
(my ide cdrom, no scsi emulation)
tom# hdparm -t /dev/hdc
/dev/hdc:
Timing buffered disk reads: 64 MB in 23.96 seconds = 2.67 MB/sec
tom# hdparm -d0 /dev/hdc (turn off dma)
/dev/hdc:
setting using_dma to 0 (off)
using_dma = 0 (off)
tom# hdparm -t /dev/hdc
/dev/hdc:
Timing buffered disk reads: 64 MB in 32.68 seconds = 1.96 MB/sec
I used the same data CD for all the tests, ran 'em several times,
included results above that were about average. So for the ide cdrom
w/no scsi emulation, dma increases IO by ~36%. While hdparm doesn't
support testing scsi drives (only ide), I suspect the performance
increase with dma enabled is similar for scsi emulated drives.
--
Tom Brinkman Corpus Christi, Texas
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