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Can't use ssd in AHCI mode-->Only in IDE

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Storage Expert

Did you do the switch the the operating system already installed? If so, the problem is because the drivers loaded into the OS are expecting the boot disk to be IDE and they won't work with the disk switched to AHCI.

See this sticky post for information on how to switch drivers for the boot disk in an already-installed system.

You can disable autorestart by tapping F8 during startup or from inside windows if you switch back to IDE. The BSOD is probably 0x0000007B which points to an unreadable hard disk. If you did not install AHCI drivers during OS install you have to manually install them and edit the registry in order for the drive to be recognized in AHCI mode.

There are instructions out there, but keep in mind the driver and registry edits vary depending on the motherboard and will probably be different from most guides unless you happen to use the same board or chipset they are using.

http://forums.pcper.com/showthread.php?t=444831

Not sure why you want AHCI mode for an SSD, but its probably not worth the trouble.
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Storage Expert

There are some AHCI optimizations over and above those possible in IDE, but in most cases I personally wouldn't bother with them. The one thing that might cause me to actually go through the steps to switch over is if I was using an SSD and I wanted to get native Windows 7 TRIM support, which I understand is only available in AHCI mode.

I'll add to sminlal's answer with a little more, the other 2 main advantages of AHCI mode, and the drive must also support these features. Hot-swap capable, and NCQ, (Native Command Queing). NCQ can be a very little faster, but that has more to do with the drive it's self than the controller.
I have tried running in AHCI mode, and eventually I just went back to IDE mode, as it is just easier, and I have not noticed even a tiny little bit of difference at all.
My drives test exactly the same with HDDTune either way.

I had the same problem. To answer your questions, yes AHCI is worth it, better transfers, trim support, NCQ, and overall better performance. In order to be able to boot from AHCi without reinstalling windows, you need to go in registry and find the msahci.sys and modify the key to 0. Google this, there should be specific instructions in order to do it. After that is done, boot, win7 will installed drivers for it automatically and everything will work fine.

Best solution

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.
By default, MS Vista and 7 have the Msahci driver disabled.

So, how to enable AHCI if you already install Windows Vista/Windows 7 using IDE interface.

Solution…(Always back up the registry key prior to making changes)

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:

HKEY_LOCAL_MACHINE\System\CurrentControlSet\Services\Msahci

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

Restart and go into the BIOS and make the changes from IDE to AHCI and restart and away you go.

I've made the change and no problems thus far, but I have not noticed any change in performance.

Hope this helps.

Excellent! I'm running in ahci mode right now. Because I have the intel x18 model drive, I don't get intel trim. So what's this about a native windows 7 trim support? i can't seem to find much information on it unless I misunderstood. How do you open the application?
Storage Expert

There's no separate application built into Windows to do the TRIM functions - it happens automatically whenever you delete files or free up space on your drive.

If your SSD doesn't support TRIM, I believe you'd have to periodically use the Intel SSD toolbox utility to inform the SSD which blocks are free so that it can perform the optimizations that TRIM would otherwise do automatically.

Folks...I got this information off the web and as such I cannot accept recognition.

Kudos should be made to 'whomever' provided the original information for enabling AHCI in Vista and Windows 7.

:bounce: 
Storage Expert

elmo2006 said:
Folks...I got this information off the web and as such I cannot accept recognition.
Maybe it's "just" from the web, but you were the one who communicated told the original poster. And I made a copy of it because it looks like it might be useful some day. Credit has gone to where it was deserved.

So say we all!


Hi folks,

Is there any workaround if you wanted to change from IDE to AHCI mode for Win XP installation?

I wanted to install second OS Win 7 in SSD as dual boot. So I thought of changing Win XP HDD installation to AHCI mode first before installing the second OS.

Specs:
Motherboard: P5Q deluxe with P45 Intel chipset
HDD Win XP installation: Hitachi Deskstar 1TB.
SSD for WIN 7 installation: OCZ Vertex 60GB

Thank you so much for the concise and clear reposting of the registry paths for this change!

You _really_ saved my HTPC installation after I purchased a new SSD. I'm now booting with no issue, and am quite happy.

Awesome sharing work! :bounce:  :D 
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