Assessing new HD over USB2 = 12.65MB/sec vs 45.39 via IDE

[rgbtxus]

Hi,
I have a new HD (WD 160GB, 8MB cache, 7200 rpm, ATA100) in a USB2.0 external case and its brother directly connected to an IDE port . The IDE drive gets 45MB/sec (hdparm -t) and the USB2.0 drive only measures 12.6. usbview shows the port running at 480Mb/sec. Since that = 60MB/sec and there were no other USB devices connected the question is why can't the USB drive keep up? Is there anyway to get better thruput?

Speaking of which is there a SCSI equivalent to hdparm? hdparm only does a few things with SCSI devices (like r, g, t, a).

Hope this can be sped up. The USB drive is for backup so I can live with it but I sort hate to lose 75% of the drive's speed without a fight!

-Dick