SATAII 4 times slower than SATA150?

In my SuSE 9.3 box I have a - Hitachi T7K250 SATAII harddrive - Samsung SP1614C SATA150 harddrive - ASUS A7N8X motherboard (with Silicon Image 3112A bios version 4.2.27) The problem is that the Hitachi drive is 4 times slower to write to than the Samsung drive - leaving the Hitachi drive unusable for capture of video from my camcorder because of too many dropped frames. Anyone know of a fix for this? Or another good place to post the problem? Thank you very much in advance.