UDMA with Kernel-2.4.3 and hdparm -X68

[mike polniak <mike@adelphia.net>]

I just got a new Maxtor HD to go along with my IBM hd. With Kernel
2.4.3 and using >hdparm -d 1 to set DMA on, i get disk reads of 30MB/sec
on the IBM. The Maxtor DiaMax UDMA (ATA 100) yields only 3 MB/sec.
The IBM is auto detected at UDMA mode4. With the Maxtor i have to
run >hdparm -X68 -d 1 to set the xfermode to UDMA mode4.But obviously
it doesn't work (the drive info still says maxDMA=0(slow)).

If i use Kernel 2.2.18pre21 the -X68 option of hdparm successfully 
enables the Maxtor to transfer at UDMA mode4 (about 33 MB/sec)
even though the drive info still reports maxDMA=0(slow).

Any thoughts on getting the Maxtor to be enabled with Kernel-2.4.3.
Is this a known issue with DMA that will change in later kernels?
Or should i just replace the Maxtor with another IBM?