Whenever a Compact Flash is present on the IDE controller, I get the following ATA error
handling messages before the IDE Linux kernel driver (pata_rdc.ko)
finally settles down (after almost a minute or so) to PIO4 speed for the Compact Flash:

I am guessing this may be due to the fact that the pata_rdc driver
does not handle all the cases (cable types and DMA modes) unlike the
Intel piix driver.