Speed measu comp 476.5x but only 16x?

I just did a burn test with nero 6. The new drive is a Sony 230E (52x)

I have tested the data image on two hard drives.
hd1 = Serial ATA drive (only drive on channel) burns at 16x because of slow data source (what?)
hd2 = IDE on primary (only drive on channel) confirmed dma mode is enabled. burns at 16x because of slow data source.

here’s the reports from the ide drive
Speed measurement completed 476.5x (71,475 KB/s_
Can olnly write at 16x instead of 24x (it’s a 52x drive)
Burn process started at 16x (2,400 KB/s)
Sony CD-RW CRX230E

Anyone know why this would be. I going to try Nero 5.5 and see if it is any better.

thanks for any help