How can I switch to AHCI Mode after installing Windows in IDE Mode?

[absic]

If you installed Windows Vista or Windows 7 in IDE Mode you can't just change the SATA controller to AHCI Mode. As you may have discovered, this will result in a BSOD and the PC will just reboot. This is due to the way that Windows is installed but you can change to AHCI Mode without reinstalling the OS though, so all is not lost. But it requires a registry tweak to get things working properly.


AHCI stand for Advance Host Controller Interface. AHCI is a hardware mechanism that allows software to communicate with Serial ATA (SATA) devices (such as host bus adapters) that are designed to offer features not offered by Parallel ATA (PATA) controllers, such as:

• Hot-Plugging
• Native Command Queuing (NCQ) -might improve computer/system/hard disk responsiveness, especially in multi-tasking environment
• If you are running an SSD then AHCI passes the TRIM commands to the drive to keep it clean and healthy.

The detailed steps from Microsoft website for switching to AHCI Mode after an IDE install are as follows:
 
• Exit all Windows-based programs.
 
• Press [Win] + R or take the RUN option from the start menu.

 
• Now type regedit there and press Enter Key to open up the Registry Editor Window.

 
• If you receive the User Account Control dialog box, click Continue.
 
• Locate and then click the following registry subkey: HKEY_LOCAL_MACHINE\System\CurrentControlSet\Services\msahci


The menu here is quite long and you have to scroll down the list about halfway to find what you're looking for.


• In the right pane, right-click Start in the Name column, and then click Modify.

 
• In the Value data box, type 0 [3 is default], and then click OK.


• On the File menu, click Exit to close Registry Editor.
 
• Restart your computer
 
• Go to BIOS and enable AHCI, Save & Reboot
 
• Another restart will be required to finish the driver installation.


If you are running Windows XP things are a little trickier but here is a really useful guide that shows you the steps you need to take: http://www.bootbeta.com/blog/guide-enable-ahci-in-windows-xp-after-installation.html


EDIT: 24/01/2013
To change Windows 8 from IDE to AHCI Mode check here: http://forum.giga-byte.co.uk/index.php/topic,6721.msg78596.html#msg78596

[Dark Mantis]

Excellent idea doing a FAQ on this absic and nicely prepared too.

+1

[absic]

Thanks DM your comments are appreciated.

I know there are a couple of other methods and that you can also download a registry file from Microsoft for making the necessary changes but this is the method that I have found to be the best way of switching things around.

[Dark Mantis]

I agree, stick to what you know and works.

[Aussie Allan]

  Nice format Absic.... well done...

  Aussie Allan

[obxeye]

tried this trick but i don't have that registry entry. running winxp pro sp3
do i need to install driver?
tia

[absic]

Taken from the foot of the original post:

If you are running Windows XP things are a little trickier but here is a really useful guide that shows you the steps you need to take: http://www.bootbeta.com/blog/guide-enable-ahci-in-windows-xp-after-installation.html

[Gloup_Gloup]

Hi absic, 

Just add infos about procedure:

Do not forgot to modify this key in Register Base:
HKEY_LOCAL_MACHINE\System\CurrentControlSet\Services\IastorV

Like you said, after...
In the right pane, right-click Start in the Name column, and then click Modify.

In the Value data box, type 0, and then click OK.

Gloup_Gloup

[Gloup_Gloup]

Hi again, 

Oupse , i do not have a possibility to modify my precedent post... so I add here...

Just a give a idea :

Make a exportation of Registry Key iaStorV, like this : AHCI_iaStorV_value_0.reg and AHCI_MsAhci_value_0.reg

Next time with this Windows (like Win7_64x, for me), you have a possibility to change a value more speedly.
Keep this *name*.reg files in the usb key, for next install of Window, by exemple.

Gloup_Gloup.

[Dark Mantis]

Hi Gloup_Gloup.

What you say makes sense in as much as it will save a bit of time and effort but hopefully you won't need to have to change it again as next time you will have it all set up for AHCI in the BIOS before Windows installation.

[Gloup_Gloup]

Hi Dark Mantis,

For me is not a problem, because before installing Windows, I make a change in Bios for AHCI parameters.

But for the inverse situation, like this topic, it is good to have informations.

In the precedent post, I have write this :
Do not forgot to modify this key in Register Base:
HKEY_LOCAL_MACHINE\System\CurrentControlSet\Services\IastorV
 
Just add : IastorV is for RAID situation. If the system have hard disk in Raid situation the value is O.
Is the situation is not RAID, like single hard drive or multiple single hard drive, the value is 3.

Now he exit too:
HKEY_LOCAL_MACHINE\System\CurrentControlSet\Services\Iastor
This is about Drivers AHCI too. So is important then value is 0  like a Key msahi.

I hope this help is util for this Topic.

Gloup_Gloup

[Dark Mantis]

Yes I see what you are getting at Gloup_Gloup and in that respect it does have validity. As you say it might help someone further on anyway.

[kristoffer]

Soooo:

Since I had Raid0 configuration which now is changed for a SSD - should I follow Gloup_Gloups directions?

Both my SSDs works nicely with "raid" selected in the BIOS, but as soon as I selects AHCI in the BIOS it just reboots at the Win7 logo.

[Dark Mantis]

Soooo:

Since I had Raid0 configuration which now is changed for a SSD - should I follow Gloup_Gloups directions?

Both my SSDs works nicely with "raid" selected in the BIOS, but as soon as I selects AHCI in the BIOS it just reboots at the Win7 logo.

From the little bit of info that you have just imparted to us there why would you want to select AHCI in the BIOS over RAID ?

[F5BJR]

*
without registry hack i use with all motherboards

if you have 2 different ports to your motherboard ex : INTEL & Marvell

connect your disk to INTEL in IDE mode ( change Marvell in RAID with BIOS )

boot

install the Marvell RAID driver

stop your computer and move your disk to the Marvell RAID port

restart , modify in your bios the INTEL port in RAID or AHCI

reboot

install INTEL Raid driver

reboot your computer

because at this time your hve the 2 * RAID / AHCI drivers installed you can start with the 2 * ports in RADI / AHCI mode

Pierre

* if your motherboard has only one sata port , you can but with an add-on bootable sata card