Re: 2.4.21 ServerWorks DMA Bugs

From: Ryan Mack (
Date: Sat Jul 05 2003 - 11:58:06 EST

That at least explains the lack of DMA, but why does non-DMA IO result in
such significant clock skew?

Also, does anybody know what the status of the failure to recognize higher
UDMA modes on the CSB5 chipset? Is there a working patch out there?

Thanks again, Ryan

On Sat, 5 Jul 2003, Markus Plail wrote:

> On Fri, 4 Jul 2003, Ryan Mack wrote:
> > I've real the other threads but nothing touches on my specific issue.
> > I have a dual P4 Xeon Dell PowerEdge 1600SC with a Fusion MPT SCSI
> > controller and a ServerWorks CSB5 IDE chipset. All the HDs are on the
> > SCSI bus, and only my CD reader and my DVD writer are on the IDE bus
> > (one on each channel). Hyperthreading is enabled (4 logical
> > processors). I am using GCC 3.2.2.
> >
> > The CD readers is the blacklisted 'SAMSUNG CD-ROM SC-148C' and I never
> > use it so I can remove it if needed. The DVD writer is a 'SONY DVD RW
> > DRU-500A'. Both are going through the ide-scsi driver. Whenever I
> > read/write CDs in the DVD writer, I get very high system load (50% on
> > one CPU), even though DMA seems to be enabled.
> If you are writing CDs with unusual block sizes (audio CDs, (S)VCDs,
> RAW mode -> blocksize != 2048) you won't get DMA with ide-scsi, no
> matter what you do. It's simply not supported.
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