How to Enable AHCI in Windows 7

What is AHCI?

For those unfamiliar with the term AHCI, it stands for:

Advanced Host Controller Interface

The explanation can be confusing and bit difficult depending on whom you ask, so the simplest explanation I found was from EVGA. According to EVGA.com, “…it is a newer technology to provide advanced features to the Serial ATA standard. It allows for access of the native functions of the SATA interface such as Native Command Queuing (which allows greater performance by optimizing how controller requests data from the hard drive) and hot swappable of SATA devices so that you may remove SATA drives from your PC without first having to shut down your computer.”

What is the difference?

SATA has two modes: IDE and AHCI. IDE is an older mode used with past devices and provides the most compatibility for the older hardware.

Do I have it?

It will depend on your hardware. You’ll need to contact your manufacturer or hardware documentation. Or do what I did and just boot into your BIOS and check.

How do I use it?

To use AHCI, Windows requires specific drivers, which are installed during Windows installation. The only problem with AHCI is it needs to be enabled in the BIOS prior to your Windows 7 installation; doing so after you have installed the OS will cause Windows not to boot. However, there is a way to enable it after windows has been installed.

WARNING: This tip requires editing the Windows registry. If you don’t know what you are doing or do not feel comfortable doing this, please do not attempt. Making changes to the registry can result in performance issues or even damage your Windows installation.

Here we go:

In the Windows start menu search box type regedit, then right-click the entry and click Run as Administrator.

 

In regedit, navigate to HKEY_LOCAL_MACHINESYSTEMCurrentControlSetservices, in the left pane click msahci, in the right-hand pane right-click Start then click Modify…

 

In the window that opens, change the value to 0 (zero) and click OK.

Close the registry editor.

A restart is needed and upon boot go into the BIOS and enable AHCI (this step will vary depending on your BIOS); when Windows boots it will finish installing the AHCI drivers.

Another restart will be necessary to finish the driver installation.

Some user experiences, that I’ve read, with changing over to AHCI claim higher Windows Experience Index (WEI) scores. I haven’t seen a jump in mine. I did clock the before and after startup time for Windows and noticed a 5 second longer boot time with AHCI enabled. This might be because of AHCI or it could just be a fluke. I’ll let you decide.

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9 Responses to How to Enable AHCI in Windows 7

  1. chieftain20 May 25, 2010 at 5:34 pm #

    I have this enabled on my computer and after a fresh re-install (for buggy reasons) my 32GB SSD Super Talent UltraDrive scores a 6.8 on the WEI, and without it enabled, I believe it scored the same as well.

    The AHCI works well for hot swapping eSATA drives. It’s not as fast as a hot swap USB drive, but its definitely faster in transfer speeds. (Although it could just be me)

    At first I had a score of 5.9 for the first test then I was like wth? So after a bit of research, CCleaner can clean the free space on your SSD and boosted my performance significantly. Its the wipe free disk space option and choose the slow 1 pass option that resets everything back to 0′s. Then pow! 6.8 again. Google it.

  2. Ron May 27, 2010 at 9:46 am #

    I tried it on my Quad-core 4 GB RAM PC with Windows 7 and the performance index declined from 5.9 to 5.2. I am not using RAID with my PC drives and both drives are in the list of drives using NCQ.
    Could this be the reason?
    “It provides no performance benefit whatsoever in a typical desktop PC. In fact having it enabled usually imposes a small performance penalty, although it too is pretty small. It is only in enterprise environments, in which access patterns are far more random than in windows, and spread out all over the surface of a drive, that any real-word benefit is derived.”

  3. Ron May 27, 2010 at 9:54 am #

    It seems this is the norm. By enabling AHCI in Windows 7, your disk performance could increase significantly if you are using a RAID drive and AHCI. Hence, it probably must be mentioned that any performance increase from enabling AHCI in Windows 7 would be in a RAID environment.

  4. Marblebardes September 10, 2010 at 10:26 am #

    I recently built a pc with a q57 intel M/B (2 dvi outputs)4 gig ram, an i5 670 cpu (has virtualization support) and are running win. ultimate with xp mode through 2 monitors.thanks to your exellent instructions I was able to get AHCI running and cut the boot time for xp from 12 secs to 4 and get snappier responses on both OSs. though the WEI scores stayed the same.I suppose the virtual XP load on the hhd (w.d. caviar green 500gb) would make any benefits gained from AHCI more obvious but the benchmark does not reflect that reality.

  5. Kriscg November 14, 2010 at 5:12 pm #

    New build P55A-G55 Intel Core i7 875K Quad Core LGA1156 2.93GHZ
    OCZ OCZ3G16004GK Gold 4GB 2X2GB DDR3-1600 CL8-8-8-24 240PIN DIMM Dual Channel Memory Kit.
    Crucial RealSSD C300 CTFDDAC064MAG-1G1 2.5″ 64GB SATA III MLC Internal Solid State Drive (SSD)
    Powercolor Radeon HD 5870 PCS+ 875MHZ 1GB 4.9GHZ

    Thanks for your exellent instructions this change over worked very smooth.
    Alto it didn’t change my over all WEI scores stayed the same 7.4 for Disk data transfer rate. Seems to be a bit faster, but who can tell at this speed.

  6. Anon911 September 24, 2011 at 10:16 am #

    Spec: Force GT 3 (backwards SATA 2)
    I did this myself today; went from 202,3 MB/sec to 265,1 MB/sec. (whole 60 MB/sec extra)- Great tutorial

  7. Burim Ramadani October 29, 2011 at 4:51 pm #

    Thanks man very useful, naw i can intaled Windows 7 and Mac os x. Thanks Thanks Thanks…!

  8. anon123 November 6, 2011 at 5:21 am #

    Works, thank you.

  9. Garrett January 6, 2013 at 1:58 pm #

    Your outlined steps worked like a charm, thanks for the tutorial and the accompanying pictures. Although the Windows Experience Index is a lot of bs, my disk data transfer rate jumped from a rating of 7.0 to 7.5 after enabling AHCI instead of IDE on my SSD.

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