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Date:      Mon, 29 Jan 2001 12:44:43 -0800
From:      Matthew Fremont <matthew@metamarkets.com>
To:        "'freebsd-questions@freebsd.org'" <freebsd-questions@freebsd.org>
Subject:   ata vs wdc for old IDE drives
Message-ID:  <86FC34EA3C4F074AA6BBFFE52ED83FED2A3C2B@METAEXCH.sfo.metamarkets.com>

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In trying to get 4.2-RELEASE running on an old machine, it appears that I'm
running into the ata DMA problems that were discussed on the questions
beginning last spring. The messages logged are like the following:

ad0: HARD WRITE ERROR blk#nnnnn
ad0: DMA problem fallback to PIO mode

This is followed by a long series of "HARD WRITE ERROR" messages. My problem
is that the fallback to PIO doesn't solve the problem.

I've also tried adding "hw.atamodes=pio,---,pio,---," to /etc/sysctl.conf,
but this didn't correct the problem either.

Hardware (circa 1997) includes:
    FIC PA-2005 main board with VIA 82C586 IDE controller
    Seagate ST21621A (supports PIO mode 4, and multiword DMA 2) as primary
      master
    MITSUMI CD as secondary master
    no primary or secondary slaves

The boot process correctly identifies the controller chipset and the hard
drive, reporting "WDMA2" in the ad0 probe message.

Using Seagate's SeaTools and format utility, I've verified that the drive
and controller are working correctly. The diagnostic tests included
successful tests of both PIO and DMA modes.

My guess is that the problem stems from an incompatibility in the ata or ad
code that occurs when the IDE controller supports UDMA/33 (according to the
ata(4) man page) but the IDE drive doesn't. 

Is this a reasonable conclusion?

I've rebuilt the kernel replacing the ata and ad devices with the obsolete
wdc and wd devices. The system booted without the errors that I observed
before.

Other than the fact that the hardware won't run the GENERIC kernel, are
there any liabilities running with the obsolte wdc and wd drivers?


Thanks,

Matthew Fremont


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