hdd performance btw ahci & ide

Before going in win 7 to decide if i have to use AHCI or IDE, I did a test for IDE vs AHCI under winXP 32.

File system benchmark
IDE drive index 83.593 Mb/s
AHCI drive index 80.737 Mb/s

IDE access time 5.93 ms
AHCI access time 5.8 ms

Physical HDD benchmark
IDE drive index 97.791 Mb/s
AHCI drive index 94.876 Mb/s

IDE access time 14.20 ms
AHCI access time 14.14 ms

This is the comparision btw IDE & AHCI, but I still have a problem unsolved with the performance of my HDD in comparision to the same time using the sandra sisoft database list. Check the following images:

1-File system benchmark IDE
2-Physical HDD benchmark IDE (read performance)
3-Physical HDD benchmark IDE (write performance)
4-File system benchmark AHCI
5-Physical HDD benchmark AHCI (read performance)

You can see that in both ways, the physical HDD benchmark of my current HDD is always slower than the identical provided by sandra (the orange one in the image 2 & 4), and that the write performance give me always that error (disk is not empty:remove all its partitions and try again), and this error happen on any HDD I have not only the main one.

The same slow benchmarks i got since the day one I assembled my PC, even I did defragmentation and the result stay the same, I tried to put it in AHCI mode and still the same, it's always slower than what it should be, any suggestions here, what did I miss, what should I do to get its best performance.

Well, I found that my drive is usually faster in IDE mode rather than AHCI. Plus, my BIOS goes through an 8+ second POST test each time for the AHCI mode...so I just leave it disabled.

As far as your drive not hitting the same numbers as the reference drive...that could be any number of things. #1) was your OS running on the drive you tested? If you tested it as a secondary drive..it would probably be faster. #2). Your motherboard and/or storage controllers obviously play an impact with how fast your drive will go. Do you really see any significant performance issues with your computer? If not, then just try not to worry about it. It's not that far off anyway.

Write tests generally cannot be performed with data on the drive or partitions defined. In order to properly write test them, they have to be a secondary drive and be totally empty.

You don't seem to realise XP is not compatible with AHCI mode. It is only supported out of the box on Windows Vista & newer versions of Windows, Linux-based systems (from kernel 2.6.19 onwards), OpenBSD (version 4.1 onwards), NetBSD, FreeBSD, OS X, & Solaris 10 (8/07 and onwards).[2] DragonFlyBSD based its AHCI implementation on OpenBSD's & added extended features such as port multiplier support. Older versions of operating systems require hardware-specific drivers in order to support AHCI. Windows XP does not provide this support out of the box.