Windows 7 - enable AHCI in Windows 7

Tyderion · 07-23-2009

hi...
i found several tutorials to enable the AHCI-driver in Windows 7/vista but the registry keys don't match mine...

the tutorial is as following:
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

but in my registry key the key "Start" does not exist and the Msahci is called msahci (though i don't think the capital letter makes a difference).
it has a "Default" value which doesn't enable the driver if set to 0 (instead of undefined (or something similar)

should i just create a value named "Start" and set it to 0 ?

thanks for helping

Edit

Tip

New Seven Forums Tutorial added - AHCI : How to Enable in Windows 7 / Vista

**johngalt** · 07-23-2009

Better read this thread first:

HOWTO: enable AHCI mode after installing Windows - PC Perspective Forums

AFAICT, you cannot change it - it needs to be set when installing. Then you'll have the correct key there, and will need to simply enable it by changing the value.

if the key is not there and you add it, it may cause your system to hang / reboot constantly / all sorts of other problems.

More details at M$ site: Error message when you start a Windows Vista-based computer after you change the SATA mode of the boot drive: "STOP 0x0000007B INACCESSABLE_BOOT_DEVICE"

Tyderion · 07-23-2009

interestingly i didn't get any bluescreen ...
i just changed bios sata-controller setting to AHCI and it just didn't boot... was there with a flashing cursor and then the display shut off (though the pc still was powered).
so i shut it down and my bios settings got changed (from a 8-multiplier to 9) and then the OC failed (logically ... can't use 9x with that vcore settings i have...)

strange... especially that the multiplier got changed ...
well back to IDE mode up and running fine

**johngalt** · 07-23-2009

not strange - it tried to boot with AHCI in the BIOS but could not - so the BIOS reset itself.

My eVGA mobo has that feature - if the machine will not boot after making a BIOS change it reverts to default setting so I can boot.

but the reason I referred you to that exhaustively long topic elsewhere was that, bottom line, if you did not install Windows with AHCI support, enabling it is going to be a PITA.

Tyderion · 07-23-2009

normally when the mobo resets it resets to "Auto" settings and not to a 400mhz bus speed with 9x multiplier...
auto settings mean 266mhz bus speed and 9x multiplier (which results in 2.4ghz)

yep i won't enable ahci ... too much trouble

**BugMeister** · 02-15-2010

- go into BIOS and check your AHCI settings
- there may be an option to "stagger" the drive identification process

- this takes a while to register, so don't be alarmed if you see a black screen to begin with..

**Bare Foot Kid** · 04-24-2010

Hello all, Seven Forums now has an easily understood tutorial on how to enable AHCI after the OS has been installed; it can be viewed at the link below.

AHCI : Enable in Windows 7 / Vista

**bearcave** · 08-02-2010

So I've tried the tutorial, when I go to regedit and to msachi the start value is already 0. So I tried enabling it in the bios and no joy. Had to switch back to IDE.

I tried downloading the matrix drivers from Intel, when I try to install them they say I don't meet the minimum system requirements.

I really don't want to re-install windows and would value any suggestions.

My system is:
Motherboard: Asus P7p55d Pro
CPU: Intel core I7 2.8ghz
Vid Card: ATI 5850
OS: Windows 7 Pro 64bit

**Bare Foot Kid** · 08-02-2010

Quote: Originally Posted by bearcave

So I've tried the tutorial, when I go to regedit and to msachi the start value is already 0. So I tried enabling it in the bios and no joy. Had to switch back to IDE.

I tried downloading the matrix drivers from Intel, when I try to install them they say I don't meet the minimum system requirements.

I really don't want to re-install windows and would value any suggestions.

My system is:
Motherboard: Asus P7p55d Pro
CPU: Intel core I7 2.8ghz
Vid Card: ATI 5850
OS: Windows 7 Pro 64bit

Post # 227

stereo · 04-12-2011

Is there any difference / improvement with AHCI vs IDE ?
Actually i tried that, i changed in the registry, but the OS didn't boot at all.
I repaired with the Windows 7 CD and now is fine.
Just wonder if i change in BIOS to AHCI and make a fresh install of OS, will that work ?