How to enable AHCI without reformating.

Posted: July 19, 2008 in Software
Tags: ,

Most current notebook nowadays allow user to set hard disk interface either AHCI (advance) or IDE (legacy). There are several reason why we should use AHCI instead of IDE. One of AHCI advantage is NCQ (Hot swappable seem not so relevan to notebook aight).
The Advanced Host Controller Interface (AHCI) is a hardware mechanism that allows software to communicate with Serial ATA (SATA) devices such as host bus adapters which are designed to offer features not offered by Parallel ATA (PATA) controllers besides higher speeds, such as hot-plugging and native command queuing.

AHCI stands for Advanced Host Controller Interface. One of the main reasons for switching to AHCI-mode is to take advantage of the NCQ-Feature of your SATA harddrive. NCQ (Native Command Queuing) allows ATA drives to accept more than one command at a time and dynamically reorder the commands for maximum efficiency. NCQ, when used in conjunction with a hard drive that supports NCQ, can increase storage performance on random workloads.

Native Command Queuing

Native Command Queuing (NCQ) is a technology designed to increase performance of SATA hard disks under certain situations by allowing the individual hard disk to internally optimize the order in which received read and write commands are executed. This can reduce the amount of unnecessary going back-and-forth on the drive’s heads, resulting in increased performance (and slightly decreased wear of the drive) for workloads where multiple simultaneous read/write requests are outstanding, most often occurring in server-type applications. However, the current technology actually slows down HD access in certain applications, like games and sequential reads & writes, because of the added latency induced by NCQ logic.

AHCI is fully supported in Microsoft Windows Vista and the Linux operating system from kernel 2.6.19. Older operating systems like Windows XP require drivers written by the host bus adapter vendor in order to support AHCI. Windows XP requires the installation of a vendor-specific driver even if AHCI is present on the host bus adapter because Windows XP was released before Serial ATA was invented.

So, how to enable AHCI if you already install Windows Vista using IDE interface.


1. Exit all Windows-based programs.
2. Click Start, type regedit in the Start Search box, and then press ENTER.
3. If you receive the User Account Control dialog box, click Continue.
4. Locate and then click the following registry subkey:

5. In the right pane, right-click Start in the Name column, and then click Modify.
6. In the Value data box, type 0, and then click OK.
7. On the File menu, click Exit to close Registry Editor

Reboot your notebook, enter bios (F2, del etc), change your hard disk interface to AHCI.

Guide on how to change AHCI setting thru bios :

Credit : Komku blog + Microsoft Support Page

  1. […] How to enable AHCI without reformating. […]

  2. […] How to enable AHCI without reformatting Windows Vista […]

  3. andri says:

    and how on XP? i dont get Msahci. should i make it?

  4. kris says:

    can you make a tutorial on how to do this on XP? i have a dual-boot installed on my 4530. i already tried this on vista and it works. how about for xp? thanks

  5. Paul says:

    Hi, thanks for the info you have saved me a re-install.

  6. Dan says:

    Hy, could you give me an advice concernig this problem: with AHCI enabled in BIOS, after booting VISTA, I want to hide or erase the irritating short DOS text that appears on POST showing the message: “BOOTING GRLDR…”

  7. arhamzul says:

    GRLDR is GRUB Loader, which is linux base boot loader.

    Either you are multi OS (windows and linux) or you use ‘pirated’ vista which use custom grub loader to mimicking oem license.

  8. SoreThumb says:

    Thanks SO much. This fixed my Vista issue– I never knew it was so simple!

    Thanks again. You .. are awesome ❤ :3

  9. Prashant says:

    Still doesnt fix anything for me. Please help! Tried lots of things! The Device Manager shows SATA AHCI under IDE controller but still there is no sign of the HDD! 😦

  10. Divas says:

    I have problem with AHCI mode now I cannot change it. Into IDE mode blue screen problem. Please tell me-How to cahnge ACHI mode to IDE mode. Help please

  11. Al Brettnell says:

    Thank you, thank you, thank you.
    I upgraded an XP laptop to Windows 7, 64-bit and forgot to change from IDE mode to AHCI mode before the install. Your registry tip saved me a day of re-installation, because I did not realize my error until I had re-loaded all of my programs. Again, thank you so much for this tip !!

  12. Ed says:

    Thanks for posting this guide for Windows 7, it worked for my 64-bit OS on my new SSD.
    Also the link to the XP version of this:
    worked great as well following it step by step.

  13. […] AHCI without reformatting, you just have to enable the driver. I found this explanation here.…t-reformating/ How to enable AHCI without reformating. Filed under: Software — expertester @ 5:29 pm Tags: […]

  14. […] File menu, click Exit to close Registry Editor 8. Enable ACHI in the bios and enjoy source…t-reformating/ […]

  15. Marius says:

    Hello, i modifide in regedit at HKEY_LOCAL_MACHINE\System\CurrentControlSet\Services\Msahci the value from 3 to 0 , but whet i restarted and enterd in bios i found that i haw no ahci option to modifie…….i have an dell gx 620 ! What do i do now? i modify the value back to 3 …..? please help me! thank you.

  16. Marius says:

    me again …mi full sistem is pentium 3 dual core 3000, 3 gh ram, 2 hdd 1 wdc wd 800jd whit the operating sistem and samsung hd 103uj , an i have windows 7 profesional os. thank you.

  17. luckybhumkar says:

    Lovely,, thanks for share! 🙂

  18. Kevin says:

    Quickest easiest way I found was to uninstall the hard drive contoller and as many as you have. Once I did that I went into the bios and set the AHCI enabled and disabled IDE. After a reboot the AHCI drivers installed and rebooted a couple of more times, so far all is fine. Worked like a charm, have been running fine for a few days, glitch free.

  19. helpware says:

    FYI – For Windows 8 the key is slightly different…


    Apparently most new computers have AHCI enabled by default

  20. molecule says:

    A what if quesiton …

    What If I enable AHCI as above, but discover that don’t like having C:\ drive on the removable list (or for if some reason I have to remove it for some peculiar cause that is unknown until it happens … not part of this thread) then how to I revert back to IDE?

    Just guessing … delete ACHI drivers from Device Manager, then boot into BIOS to change AHCI to IDE, then reboot into Windows, which then finds new hardware and installs?

    (Actually, I’m using XPpro sp3, but that that post is old, and as an issue that is hopefuly moot, since whatever the OS it will have both native IDE and Intel AHCI drivers available …)

    thanks …

  21. Seems like you truly know quite a bit about this specific
    subject matter and that demonstrates as a result of this specific article, given the name “How to enable AHCI without reformating.
    Expertester”. Many thanks -Bettie

  22. j.m.d.k. achternaam says:

    Enabling AHCI on existing Windows XP installation.

    1. Download Intel Sata RAID/AHCI storage driver floppy (used during Windows setup with F6) from your motherboard manufacturer and extract files to a directory on your HD.

    2. In device manager change existing IDE ATA/ATAPI controller:
    a. open IDE ATA/ATAPI controllers (click on +)
    b. right click the first Intel controller listed
    c. select “Update driver…”
    d. select “No, not this time, Install from a list or specific location (Advanced)”
    e. select “Don’t search. I will choose the driver to install”
    f. select the Standard Dual Channel PCI IDE Controller and click Next (do not reboot)
    g. repeat steps c. to f. for the second controller

    3. Reboot.

    4. In device manager, update the drivers for the existing IDE ATA/ATAPI controller:
    a. open IDE ATA/ATAPI controllers (click on +)
    b. right click the first Standard Dual Channel PCI IDE Controller
    c. select “Update driver…”
    d. select “No, not this time, Install from a list or specific location (Advanced)”
    e. select “Don’t search. I will choose the driver to install”
    f. click on “Have disk” and browse to the directory with the AHCI drivers
    g. select the iaAHCI.inf and click Next
    h. ignore any warnings and reboot

    (If you get a blue screen and the system reboots during these steps, repeat them for the second controller)

    5. Reboot

    6. Enter system bios and change controller to AHCI and save.

    Your system should now run in AHCI mode.

    Possibly you can install the Intel Matrix Storage Manager. Although I’m not sure, it might improve performance.

  23. Shaharuddin says:

    These comments are awesome! After 3 weeks looking for the solutions how to resolve BSOD when this bios setting automatically changed from IDE to AHCI. TQVM

  24. Herta Keets says:

    Cool site. Cheers for sharing.

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