Re: hdd: misaligned DMA buffer

Andre M. Hedrick (hedrick@astro.dyer.vanderbilt.edu)
Wed, 2 Sep 1998 23:59:34 -0500 (CDT)


On Wed, 2 Sep 1998, Sang Kang wrote:

> Hello,
>
> Under 2.1.119, I got the message "hdd: misaligned DMA buffer" while
> I'm just cp'ing files from my hard drive to a md0 drive. since the
> error is originated from hdd, which is my boot partition, I assume
> it's got to do with my harddrive (6.4G, DMA/33 running on embedded
> EIDE controller, MAXTOR).
>
> Would anyone kindly explain what this mean?
>

Your hardware may have a non-standard entry point for the DMA request
mapping. If you exceed the 64kB boundaries, you may/will rupture
the table. This is unlikely.

My past experience with a 6.4G Maxtor (Diamond Series UDMA/33) was a so
bad that I sent it back. I replaced it with a WD 6.4 UMDA drive. This
was a mixed HD pair of a WD DMA mode 2 with a Maxtor UDMA mode 2.
WD primary and Maxtor secondary on a PIIX3 ide0.

Try this silly test of hunting down timing errors.
Recompile the kernel as a 386 and see if it goes away. If it does, repeat
as a 486 and continue the process until you see the failures begin again.
If they get progressively worse, you have a major timing problem and
incompatable hardware combination. Solution, juggle the device
combinations, preferred is to switch to Quantum UDMA drives.

First, would you supply a description of your hardware, before we start
with the tests above. Since these tests can be "DISTRUCTIVE" to the
filesystem.

Regards,
Andre

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