[root@localhost ~]# hdparm -Tt /dev/hda

/dev/hda:
Timing cached reads: 558 MB in 2.00 seconds = 278.31 MB/sec
Timing buffered disk reads: 110 MB in 3.01 seconds = 36.50 MB/sec
For those who read my original thread:

http://www.phoronix.com/forums/showthread.php?t=3424

It was the CF/IDE adapter itself. It didn't properly support UDMA.