[6214] in linux-scsi channel archive
Re: Probably a silly problem ..
daemon@ATHENA.MIT.EDU (Richard Robinson)
Tue Mar 30 11:34:11 1999
Date: Tue, 30 Mar 1999 15:35:25 +0100 (BST)
From: Richard Robinson <richard@beulah.demon.co.uk>
To: linux-scsi@vger.rutgers.edu
In-Reply-To: <199903292016.PAA31956@cutter-john.mit.edu>
On Mon, 29 Mar 1999, Monty wrote:
> >> Warning: Running low on SCSI DMA buffersWarning: Running low on SCSI DMA
> >> buffersWarning: Running low on SCSI DMA buffers
> >> etc etc, hundreds of times over.
> >
> >Hm, it seems that the buffer is running low which might end in a write-error
> >(buffer underrun)... You are using the aha154x; I think there is an option in
> >the BIOS of the controller to choose the DMA-channel... (on 1542 there is).
> >Make sure that the channel (I think default is DMA 6) is not in use by
> >another device which has direct memory access (soundcard and so on).
>
> I believe this has nothing to do with the DMA channel. If I recall
> Doug Gilbert's DMA/memory rants properly, ISA SCSI cards have to do
> DMA under the 16MB level, and Linux 2.2 memory management is so
> aggressive about managing higher memory, that it leaves almost no
> space under 16M for ISA DMA. His quote is "the more RAM you have, the
> less space you have under 16M" or something exactly to that effect.
>
> Downgrade to 2.0, invest in a PCI SCSI adapter, or convince the VM
> tuning folks that they did a Bad Thing (tm)....
I hadn't known of this 16M limit. It almost looks like an explanation,
except that I haven't gone to the 2.2.x series yet, this is with 2.0.36
--
Richard Robinson
"The whole plan hinged upon the natural curiosity of potatoes" - S. Lem
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