v> I can make one for you, but first I'd like to find out what exactly are
v> the problem cases.

I have a VT82C686 motherboard.  It has one UDMA-100 slot and two
regular IDE slots.  I have an IBM DTTA-371440 (about 18 months old) as
hda (only fat32 filesystems), and an IBM DTLA-307030 as hde
(i.e. plugged into the UDMA-100 slot).  I've never seen any problems
with DMA on the newer drive, but if I turn on DMA and do anything with
the older drive, I get stuff like this:

  /dev/ide/host0/bus0/target0/lun0:hda: dma_intr: status=0x51 { DriveReady SeekComplete Error } 
  hda: dma_intr: error=0x84 { DriveStatusError BadCRC } 
  hda: dma_intr: status=0x51 { DriveReady SeekComplete Error } 
  hda: dma_intr: error=0x84 { DriveStatusError BadCRC } 
  hda: dma_intr: status=0x51 { DriveReady SeekComplete Error } 
  hda: dma_intr: error=0x84 { DriveStatusError BadCRC } 
  hda: dma_intr: status=0x51 { DriveReady SeekComplete Error } 
  hda: dma_intr: error=0x84 { DriveStatusError BadCRC } 

The driver attempts to reset ide0 a few times, gets more of the above,
then gives up with an I/O error.

I've been seeing these problems as long as I've been tracking the 2.3
series, up to and including 2.4.0.  I can't boot a 2.2 kernel on this
machine to compare, as it doesn't recognise hde (which is where Linux
lives).

Here's the output of lspci under 2.4.0, in case it's useful:

  00:00.0 Host bridge: VIA Technologies, Inc.: Unknown device 0305 (rev 02)
  00:01.0 PCI bridge: VIA Technologies, Inc.: Unknown device 8305
  00:04.0 ISA bridge: VIA Technologies, Inc. VT82C686 [Apollo Super] (rev 22)
  00:04.1 IDE interface: VIA Technologies, Inc. VT82C586 IDE [Apollo] (rev 10)
  00:04.2 USB Controller: VIA Technologies, Inc. VT82C586B USB (rev 10)
  00:04.3 USB Controller: VIA Technologies, Inc. VT82C586B USB (rev 10)
  00:04.4 Host bridge: VIA Technologies, Inc. VT82C686 [Apollo Super ACPI] (rev 30)
  00:09.0 CardBus bridge: Texas Instruments PCI1225 (rev 01)
  00:09.1 CardBus bridge: Texas Instruments PCI1225 (rev 01)
  00:0a.0 Ethernet controller: Lite-On Communications Inc LNE100TX (rev 20)
  00:0b.0 Multimedia audio controller: Creative Labs SB Live! EMU10000 (rev 08)
  00:0b.1 Input device controller: Creative Labs SB Live! (rev 08)
  00:11.0 Unknown mass storage controller: Promise Technology, Inc.: Unknown device 0d30 (rev 02)
  01:00.0 VGA compatible controller: nVidia Corporation: Unknown device 0150 (rev a3)

If you need any more information, I can dig it out.

	<b
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