Cannot enable it, hence my DVD playback is choppy (audio/video stalls every 2-3 sec).

When i run "hdparm -d1 /dev/dvd" as root, I get:

HDIO_SET_DMA failed: Operation not permitted

Running RH8 with default kernel...DVD drive supports native UDMA2, it reports it in the POST screen.

Any ideas?

You may put into /etc/modules.conf this line:

options ide-cd dma=1

Thanks got it