Re: Problems with scsi emulation

From: Douglas Gilbert (
Date: Sun Jun 01 2003 - 23:55:06 EST

> 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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