Re: 2.1.111: IDE DMA disabled?

Mark Lord (
Tue, 28 Jul 1998 20:16:09 -0400

Linus Torvalds wrote:
> And yes, he couldn't reproduce it at will without SMP. Which may mean that
> there is a SMP problem, but is equally likely to mean that with SMP

Duh. Letmesee.. SMP=1 by default.. Mmmm... looks very bad.

On a constructive note, could there be an SMP cache-sync problem
with DMA (IDE or SCSI) ?

SMP really should be OFF by default,
especially as SMP kernels do not survive
booting on many non-SMP machines.

> And yes, in the Free/NetBSD camp it _is_ acceptable to say "don't use too
> long a cable".

That's from the IDE (ATA) specs. 18" max.

The timings with DMA are *identical* to the timings with PIO,
so if it fails with DMA, it will fail with PIO as well.

Removing DMA from the kernel solves nothing there.

The Linux IDE guy

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