Understanding DMA/NoDMA options and fixes

[Nathaniel Husted]

On 7/19/05, John Best <jbest at insightbb.com> wrote:
> -----Original Message-----
> From: fedora-list-bounces at redhat.com
> [mailto:fedora-list-bounces at redhat.com]On Behalf Of Paul Howarth
> Sent: Tuesday, July 19, 2005 1:53 AM
> To: For users of Fedora Core releases
> Subject: Re: Understanding DMA/NoDMA options and fixes
> 
> 
> On Mon, 2005-07-18 at 21:02 -0500, John Best wrote:
> > I think I asked this before , but I am still not satisfied with the
> > answer...
> >
> > I have had to boot with the nodma option since FC3...   I have not had
> > issues doing this, but I wonder if I am getting the performance I should
> > by disabling the dma option (I have seen posts that have pointed that
> > nodma can reduce linux performance on some machines).   The question
> > that I have not resolved is what can I do about it?????
> 
> The ide=nodma option is usually suggested as a workaround for mediacheck
> problems during installation; systems installed that way will have the
> same option configured in grub but it *may* not be necessary for normal
> operation. Does your system work if you boot without that option?
> 
> Paul.
> --
> Paul Howarth <paul at city-fan.org>
> 
> Based on past experiences, no it does not boot correctly.. My problems did
> not seem to be media check related.
> Both the install boot and boots following install would hang at a particular
> location ( I never was able to track down, but if I recall it was just near
> or after the kernel load).  Using NoDMA corrected it and I have been using
> it since FC3..(possibly back to fc2)  Once and a while I build a boot disk
> (Using re-writable cd's) to check it out without the ide=nodma option and in
> all cases appears to hang at a spot during the boot.
> 
> My thought was that if this is a hardware component/connection issue, I
> could try to correct or possibly at least see which component (Disk drive or
> cd ) was the culprit... Currently running with 2 HD (I think a west Dig 160G
> and a Maxtor 40g)  and 1 CDRW (HP) and 1 CDROM (Generic).  Thinking there
> may be jumpers that will enable/disable the appropriate issue causing dma
> setting on the device.. (OR BOIS???)
> 
> Anyway, I may try to boot without the nodma option and see if I can track
> down where it hangs up...If that might help with a firmer diagnosis.
> 
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> 
I am unsure of how much help this might be to you, but I had an issue
where I would get a kernel panic very early in the FC boot process.
Setting ide=nodma at boot fixed the problem. It turned out that the
rounded cable I was using was damage, and when I replaced the cable
things booted fine.

Cheers,
Nathaniel Husted