Enabling AHCI in Windows 7

Most modern motherboard with integrated SATA controllers offer a few options for accessing connected drives- usually these choices are ATA, RAID or AHCI.

ATA is a basic interface and it works well with older operating systems (such Windows XP). This emulation is good as you generally don’t need to load additional controller drivers while installing windows (F6 during bootup)

RAID offers different disc configurations for redundancy and/or performance- and generally requires a driver to setup Windows.

Advanced Host Controller Interface (ACHI) is a newer implantation that allows for SATA drive hot plug and supports native command queuing (NCQ). This can have some performance benefits to Widows Vista/7. Most board that support SATA II drives will have this option- it should definitely be an option on the Intel x58 and P55 motherboards…

I found some info about converting an ATA install to AHCI on I Think Different and the PC Perspective forums.

If you installed Windows 7 on an ATA configured drive (like I did), you don’t need to re-install the OS again; a small registry tweak will enable the AHCI driver and Windows will re-detect the drive on next boot up.

The registry key is located in:

HKLM\System\CurrentControlSet\Servuces\msahci.

The Key is a reg_dword named ‘start’. In non-AHCI system, this is set to ‘3’. To enable the AHCI driver, this needs to be changed to ‘0’.

After the above change is made, make sure all of your data is backed up, reboot into BIOS and change the SATA controller from IDE to ACHI. Reboot back into Windows 7, let windows re-detect the drive, reboot again and you should be using AHCI! :)