Let's do another synthetic test, SiSoft Sandra, just to see if we can match the results we've seen in HDTach.

What SANDRA also does (important for an HDD) is to test at several positions of the HD. See, at the outer part of a platter the performance is slower. The drive index test is what I refer to. The higher the better.

The WD Velociraptor is fast at 99 MB/sec and then the Vertex 2 shows performance up to 232 MB/sec speeds. Sandra returned a write speed of 201 MB/sec

This matches the HDTach results really well.

Once again when we enable AHCI mode, activate drive offset 4 and the Matrix Storage driver then read performance jumps up bigtime.

As you can see that's much better at 263 MB/sec .. unfortunately write performance now drops below 200 MB/sec. A weird kind of tradeoff but likely fixed with upcoming firmware updates.