Improve SATA hard disk performance (Convert from IDE to AHCI)

Every hard drive in a modern computer is connected to the system through a storage controller. This controller typically can communicate with the hard drive via a number of different interface protocols. For maximum compatibility many computers are configured in the BIOS to use the older IDE interface protocol to communicate with modern SATA hard drives. This setting is acceptable for the average computer user but IDE lacks support for new technologies such as native command queuing (NCQ) and hot-plugging hard drives (add or remove drives without restarting the computers).

Intel invented a new storage controller interface known as AHCI (Advanced Host Controller Interface) that supports these new technologies with modern SATA hard drives. If you have a hard drive that supports NCQ, it is worth a try to see if your disk performance improves with your workload.

The main problem preventing users from changing the storage interface protocol from IDE to AHCI in the past has been blue screens that could only be cured by undoing the BIOS change or reinstalling Windows. The cause of the problem is the mass storage driver installed when Windows was first setup. Since IDE was enabled at install only the IDE storage driver was configured in Windows. With the AHCI driver missing, Windows cannot read from the hard drive and throws a BSOD with error code 0x0000005B.

Now there is an easy solution that will allow you to switch between IDE and AHCI in the bios and Windows will boot without any problems. The key is to enable the AHCI driver in Windows before you make the setting change in the BIOS.

For most users this will work:

1. Open Registry Editor and navigate to HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\services\msahci.
2. Right click on the Start registry DWORD and select Modify.
   
3. Set the value to 0 and click OK.
   
4. Now the Start setting should be set to 0.
   
5. Reboot and enable the AHCI setting in your BIOS.

If you are using a RAID adapter or other interface try the following:

1. Open up Registry Editor and naviage to HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\services\iaStorV OR HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\services\iaStor.
2. Repeat the steps above.

Not all users will see a major performance improvement with AHCI and a SATA hard drive but NCQ can be very helpful under the right workload. Post your experience and setup in the comments below.

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