AHCI : Enable in Windows 7 / Vista

AHCI : Enable in Vista and Windows 7 after OS install​

   Information

AHCI Advanced Host Controller Interface makes NCQ Native Command Queing along with hot-plugging or hot swapping through SATA Serial-ATA host controllers possible; Vista was the first to offer this feature. The issue with AHCI is it needs to be enabled in the BIOS prior to OS installation; doing so after you have installed the OS will disable the PC. The reason why is Windows disables the AHCI drivers not needed durring installation.

This tutorial will show you how to enable AHCI after you have installed the OS if you didn't already have AHCI enable in the BIOS when you installed the OS.

   Warning

Changing values in the Windows registry can disable your machine; if you're not sure how to do this please post a question in this tutorial and someone will be glad to help you.

   Note

This method will also work for Windows Vista though the default DWORD string value in Vista will be "4" where it will be "3" in Windows 7.

As a precaution it would be a good idea to create a "System Restore Point" before you start this, the tutorial can be found at the link below.

System Restore Point - Create

Let's get started!
1) In the Windows start menu search box type regedit, right click the entry, click Run as Administrator, enter your user credentials for the UAC prompt, then click yes to open regedit.



2) In regedit navigate to HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\services.

3) In the left pane, click on msahci, in the right pane double click on Start to modify it.


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

5) In the left pane, click on iaStorV (if there), in the right pane double click on Start to modify it. Repeat step 4, and go to step 6 below.
NOTE: From: Error message occurs after you change the SATA mode of the boot drive

6) Close Registry Editor.
7) Now you'll need to restart the PC and go into the BIOS and enable AHCI. When Windows boots up, it will finish installing the AHCI drivers.



8) You will need one final restart to finish the process after the drivers are installed.

   Note

For those with nForce boards, have a look at the Information post below.

The method was worked out by Everlong and credit for that goes to him, thanks mate!

Enjoy!

Related Tutorials

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• How to Enable AHCI in Windows 8 and Windows 10 after Installation
• How to Enable HIPM and DIPM for your SSD and HDD in Windows 7

 

[belikexp]

Ok great tutorial and works except....
I reran the assessment for the hard drive and received this..
Do I uninstall a driver?

 

[Bare Foot Kid]

Hello belikexp.


Did it list the driver causing the problems?

 

[belikexp]

None that I noticed. Did a google search someone mentioned enabling write cache but that doesnt make sense. It is enabled though.
I'll reboot and run again.

 

[belikexp]

After setting the registry; rebooting and setting the AHCI in the BIOS. If you re-run the assessment it only ran the hard drive only. The secound time rebooting I ran the assessment again and it ran the whole series of tests. No errors. So we need to reboot twice?
I saw no improvement for Sata hard drives.

 

[Bare Foot Kid]

After setting the registry; rebooting and setting the AHCI in the BIOS. If you re-run the assessment it only ran the hard drive only. The secound time rebooting I ran the assessment again and it ran the whole series of tests. No errors. So we need to reboot twice?

Yes, change the reg entry and reboot to change the BIOS then install the drivers then reboot again to finish; so you got it sorted?

 

[belikexp]

After setting the registry; rebooting and setting the AHCI in the BIOS. If you re-run the assessment it only ran the hard drive only. The secound time rebooting I ran the assessment again and it ran the whole series of tests. No errors. So we need to reboot twice?

Yes, change the reg entry and reboot to change the BIOS then install the drivers then reboot again to finish; so you got it sorted?

Actually I had to reboot once more. Then everything is fine.

 

[Bare Foot Kid]

After setting the registry; rebooting and setting the AHCI in the BIOS. If you re-run the assessment it only ran the hard drive only. The secound time rebooting I ran the assessment again and it ran the whole series of tests. No errors. So we need to reboot twice?

Yes, change the reg entry and reboot to change the BIOS then install the drivers then reboot again to finish; so you got it sorted?

Actually I had to reboot once more. Then everything is fine.

At least you got it. thanks for the update.

 

[atlcraig]

Thanks for the help. One other question, since I already have Windows 7 installed and I didn't haveAHCI turned on the drivers weren't loaded. How do I get the drivers loaded now? Thanks again for the help, Atlcraig

 

[Dave76]

hello,
isnt it possible to have raid and ahci activated at the same time??

Raid actually runs under AHCI, If you want to continue using RAID don't change to AHCI.

You can run in RAID with no drives in actual RAID, and get the benefits of AHCI.

Many SATA controllers offer selectable modes of operation: legacy Parallel ATA emulation, standard AHCI mode, or vendor-specific RAID. Intel recommends choosing RAID mode on their motherboards (which also enables AHCI) rather than the plain AHCI/SATA mode for maximum flexibility, due to the issues caused when the mode is switched once an operating system has already been installed.[2] Legacy mode is a software backward-compatibility mechanism intended to allow the SATA controller to run in legacy operating systems which are not SATA-aware or where a driver does not exist to make the operating systems SATA-aware.

 

[atlcraig]

I have changed the setting with regedit and created a restore point in windows 7. I then went into the BIOS and enabled AHCI. When I booted the system up after that I got themessage ERROR LOADING OS and now can't get the computer to boot. I had to get on one of my other computers to get back here. I need help now. Can anyone give me an idea on what I need to do now?????

 

[Dave76]

Which HDD is your boot drive? SATA or IDE?

When you changed the BIOS setting from IDE to AHCI did you save & exit?

Don't know much about AMD AHCI drivers besides reading that some people are having trouble with them.
Some are using the Intel AHCI drivers and reporting success.

Did you try booting to safe mode?

If this doesn't work, start your computer, go to BIOS set it back to IDE mode and see if it will boot.
If it does boot, it means your AHCI drivers were not loaded on the previous attempt to switch to AHCI mode.

 

[Bare Foot Kid]

Which HDD is your boot drive? SATA or IDE?

When you changed the BIOS setting from IDE to AHCI did you save & exit?

Don't know much about AMD AHCI drivers besides reading that some people are having trouble with them.
Some are using the Intel AHCI drivers and reporting success.

Did you try booting to safe mode?

If this doesn't work, start your computer, go to BIOS set it back to IDE mode and see if it will boot.
If it does boot, it means your AHCI drivers were not loaded on the previous attempt to switch to AHCI mode.

Hello again atlcraig.


Dave has listed some very good things to check on, here is the tutorial on safe mode, be sure to post back to keep us informed.

 

[atlcraig]

Dave76,

I have 4 SATA drives, one of which is my C drive. I did save the changes in the BIOS.

It looks like the AHCI drivers were not loaded.

I was able to boot into safe mode, but only when I used my Windows 7 64 bit DVD. When I tried to reboot without using the Windows 7 disc I still get the message Error Loading OS.

When I changed the BIOS back to IDE and tried to reboot without the system disc I whould get the same message.

I think you are right that the AHCI drivers were not loaded. I am not sure where to go from here next. I may have to call Microsoft and see if they will/can help me. I think that since they had nothing in the documentation that came with the system I really think it is a Microsoft problem and that they should help anyone having this type problem. We'll see if they think the same way.

Thanks for the help. I still can't get the computer to boot without having the Windows 7 setup disc in the computer.

atlcraig

 

[atlcraig]

Dave76

One other thing - I am not running raid and do not want to. For AHCI to work do you have to be running raid? It was my understanding that you didn't have to. Do you know if this is correct? Thanks again for the help - atlcraig

 

[WindowsStar]

Question: Do these steps work for Windows XP Professional as well?

 

[Dave76]

Dave76

One other thing - I am not running raid and do not want to. For AHCI to work do you have to be running raid? It was my understanding that you didn't have to. Do you know if this is correct? Thanks again for the help - atlcraig

The answer is NO, you do not have to be in/using RAID for AHCI to work.
AHCI is a separate function from RAID, actually selecting RAID will put the computer in AHCI mode.

Your choices in BIOS are IDE, AHCI or RAID mode.
When you set your computer to RAID (normally the third option in your BIOS) it will set it to AHCI mode.
You can set your computer to RAID (which uses AHCI mode) and not have any HDDs set up in RAID configuration. You will have the advantages of AHCI when in the RAID setting.

The main benefits of AHCI are your HDDs can be HotSwappable (plug and play and unplug, without shutting down the computer), NQR (native command queuing, this allows your HDD to run more efficiently), allows the use of S.M.A.R.T. the HDD monitoring software.

Some people say it will provide a slight, noticeable, speed improvement, I did see an improvement by enabling mine. Also required for SSDs to use Trim function.

AHCI is:

Advanced Host Controller Interface (AHCI) is an application programming interface defined by Intel which defines the operation of Serial ATA host bus adapters in a non-implementation-specific manner. The specification describes a system memory structure for computer hardware vendors to exchange data between host system memory and attached storage devices.

Read the wikipedia site linked below and it will explain what AHCI is.

Click here >> Many SATA controllers offer selectable modes of operation

 

[Bare Foot Kid]

Question: Do these steps work for Windows XP Professional as well?

Hello WS.


No they do not, XP will not boot when AHCI is enabled in the BIOS, it'll blue screen; when I was booting XP and Windows 7 I had to change back and forth between AHCI and IDE mode depending on the OS I wanted to boot to.

 

[atlcraig]

Dave76,

I have found what my problem is and that is that after I enabled AHCI for some reason it changed the sequence of my drives. I am able to go into the BIOS and select the drive that I want to boot from and everything works just fine.

I had to try each of the drives until I found the right one! I have 4 SATA drives and 2 IDE drives and 14 partitions. I am now trying to find out why the boot drive that the system was using before AHCI was installed was changed because I don't want to go into the BIOS and make the change each time I boot the system. If anyone has an answer to this question I'm all ears!

Thanks again to every one for all the help. This is agreat web site and I am sure glad I found it.

 

[Bare Foot Kid]

Hello again atlcraig.



Change the boot priority in the BIOS to boot from the HDD you need it to boot from, have a look at the tutorial at the link below; be sure to post back to keep us informed.

Boot Priority - Change - Vista Forums

 

[atlcraig]

Bare Foot Kid,

thanks for the help.

I found mine under the BOOT heading and then under HARD DISK DRIVES. The instructions said to use the arrow keys to select the drive you wanted to move and then use the + to move it up and – to move it down. When I tried that nothing happened. I then tried the Pg Up and Pg Dn keys and they worked! I now have all of the drives in the right order and the system is now booting up just fine. I’m glad you found where to do the change and that made me look until I foun the place to make the changes on my computer.

atlcraig