SATA Drive Speedup

HDTach shows 49 MB/s average read…

My 10,000 rpm, 36 GB SATA drive test results from HDTAch are:

Burst: 100 MB/s
Random Access: 8.6 ms
CPU Util: 2%
Ave Read: 49.7 MB/s

The drive is capable of 150 MB/s. I have the latest drivers for my card which uses SiIG 3112 chip. Any suggestions?