Message-ID: <3EDAD8AA.50503@interlog.com>
Date: Mon, 02 Jun 2003 14:55:06 +1000
From: Douglas Gilbert <dgilbert@interlog.com>
Reply-To: dgilbert@interlog.com
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To: linux-kernel <linux-kernel@vger.kernel.org>, agusmdp@hotmail.com
Subject: Re: Problems with scsi emulation
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 > I'm using a customized 2.4.20 kernel (red hat 9) with
 > scsi emulation, scsi  cdrom & scsi generic support
 > options enabled in .config and hdx-ide-scsi in
 > lilo.conf. apps as cdrecord or cdrdao take up all my
 > cpu time (I have a duron 1.1 gz, kt133, 192mb sdram,
 > 30 gb 5400 rpm hd). in windows (with dma enabled) Nero d
 > oesn't take up any (or almost) cpu time...
 > is this an issue of the linux-kernel or a configuration
 > problem?

Due to many problems with DMA locking up on ATAPI writers
earlier in the lk 2.4 series, Linux takes a very
conservative approach and turns off DMA.
It can be turned back on with:
  # hdparm -d 1 /dev/hdb
assuming your cdwriter is found at /dev/hdb (even
though the ide-scsi driver "owns" that device
and you address it as /dev/scd0 ). You can get
faster DMA modes with the addition of the "-X"
switch in hdparm but that should not be necessary.

Doug Gilbert

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