AHCI stands for Advanced Host Controller Interface, which is a new hardware communication standard from Intel that can significantly improve the performance of SATA drives. One of the best AHCI features is Native Command Queuing (NCQ). With NCQ your hard drive can decide in which order to read and write data. This way your computer can access the data from one area of the drive before moving to a different part of the disk. This way data is opened in one smooth move and the hard drive's read head doesn't have to move all over the place. This reduces wear and tear, noise, and improves performance.
Windows XP users: AHCI drivers are not included on the Windows XP and earlier installation CDs, as AHCI was developed long after the release of Windows XP. To enable the AHCI mode, you need to use a driver floppy and the F6 method when installing Windows XP. Otherwise your hard drive won't be detected. However, it is still possible to enable AHCI without reinstalling your XP. Just update the IDE driver through Device Manager and change your SATA Mode to AHCI (instead of IDE) in the BIOS.
Windows Vista and 7 have native AHCI support, which is great. The not-so-great thing is that most likely your system doesn't have AHCI enabled in the BIOS, which means that Windows simply does not know that it can use AHCI.
First of all, you'll need to check if you have AHCI installed by doing the following:
- Click on Start and type Device Manager in the search box.
- In the Device Manager, expand the IDE ATA/ATAPI Controllers section.
- Look for Standard AHCI 1.0 Serial ATA Controller. If it's there, then your system is already using AHCI. If not, we'll need to enable it.
As a rule, AHCI support needs to be activated in your BIOS, but only before you install Windows. Otherwise you risk ending up with Blue Screens of Death, which will eventually require a reinstall. Fortunately, it's possible to avoid this by editing the registry prior to activating AHCI support. Here is how to enable Microsoft AHCI driver in the Windows 7 registry:
- Click on Start and type regedit in the Search box to open Registry Editor.
- Navigate to HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\services\msahci and expand it
- In the right-hand pane, locate the START key
- Set its Value to 0 (zero)
- Close Registry Editor.
- Alternatively you can change the value under HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\services\iaStorV to enable the Intel RST driver.
The results differ from system to system, so you'll need to experiment a bit and check which driver works better for you, msahci (Microsoft AHCI) or iaStor (Intel RST). I recommend using AHCI, but you can always revert to the IDE driver if AHCI wasn't fast enough for you.
Now you can reboot your computer and enter the BIOS where you can enable AHCI.
The specific instructions vary from manufacturer to manufacturer, so you'll need to consult your support documentation. Once you've found the required setting and activate AHCI, save all changes and reboot your PC. Windows will install the needed driver upon reboot, which you can later confirm through the Device Manager. You might need to reboot once more to activate the driver.