Mitch Wheat - Treat the cause, not the symptoms!

During a lunch time conversation with a colleague (Thanks Hadley!), it was mentioned that most PC setups are not utilising their hard disk speed potential due to being configured as IDE instead of AHCI. I’ve previously tried to get this working under Windows XP but it required a re-install and went into the too-hard basket.

The good news is, if you are running Windows 7 (or Vista, but let’s hope it’s the former!), ACHI is supported out of the box and you do not need to re-install.

You might be thinking that this doesn’t apply to you if you have a shiny new SSD? It does!  Back in August this year, I blogged about the Windows 7 performance score and how I was a little disappointed with the disk performance as it was the ‘slowest’ component in my new system.

How to Activate AHCI

These instructions are for expert users and are at your own risk. [If you installed Windows 7 with your motherboard BIOS set to use AHCI rather than IDE, then Congratulations! there is nothing to do.]

Otherwise, there are two things you need to do to activate AHCI.

1. You must Activate AHCI in Windows First

• Close all open programs.
• Open regedit and navigate to the key: HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\services\msahci
• Double-click on the ‘Start’ value to edit it. The value will most likely be “3″. Change that value to “0″ (zero).
• Close regedit, and reboot your PC.

2. Activate AHCI in your Motherboard BIOS

• As your PC boots up, enter your BIOS setup.
• Go to the hard disk configuration. Find the setting that says SATA Setting or configuration (varies by motherboard).
• Select AHCI from the drop-down options. Once it’s set to AHCI, save and exit, and continuing booting Windows.
• Windows will install the necessary drivers and then prompt you to reboot.
• Re-boot and you are done!

If you don’t activate it in Windows first, you will get a blue screen upon loading Windows. If that happens, go into your BIOS and set SATA mode back to IDE, then boot Windows, and follow the steps as described above.

Please Note: this won’t work if you are already using RAID as your SATA setting, unless your motherboard has a second dedicated RAID controller like mine (many do).

Here is the re-run Windows Experience index:

And you know what? It’s not just faster by the benchmark score; it is noticeably faster accessing the disk as well!