Re: IDE DMA problems on 2.4.0 with vt82c686a driver

Mark Hahn (hahn@coffee.psychology.mcmaster.ca)
Thu, 11 Jan 2001 09:41:55 -0500 (EST)


> Since this looks like either a chipset, drive, or driver problem, I am

no: the only entities involved with udma crc's are the drive,
the controller (and the cable). the kernel is not involved in any way
(except to configure udma, of course.)

> occasionally (not often/constant, but sometimes) get CRC errors:
> hda: dma_intr: status=0x51 { DriveReady SeekComplete Error }
> hda: dma_intr: error=0x84 { DriveStatusError BadCRC }

nothing wrong here. occasional crc retries cause no performance impact.

> After reading some archives in linux-kernel, I tried changing some
> options. Then I changed out the 40 pin, 80 wire cable with a new one.

great, since without the 80c cable, udma > 33 is illegal.
is it safe to assume your cable is also 18" or less, with both ends
plugged in (no stub)? you might be able to minimize CRC retries
by changing where the cable runs. it's also conceivable that CRC
errors would be caused by marginal power, bad trace layout on the
motherboard, and definitely by overclocking (PCI other than 33 MHz).

> My main concern that I havnt beem able to find an answer for on any
> archives or documentation, Can this cause file system corruption in any way?

abosolutely not. udma checksums each transfer. when checksums don't match,
the *hardware* retries the transfer (and incidentally reports the event,
which Linux obligingly passes on to you.)

regards, mark hahn.

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