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Windows 7 : AHCI Enabled / Disabled.

N

NoobyDoo

Senior member
I have two primary partitions : one with WinXP Pro which I used for a long time, the second with Win7 Ultimate 64-bit which I have migrated to. I use GAG as a boot loader. Both are totally independent of each other.

WinXP was installed with AHCI disabled. But Win7 was installed with AHCI enabled. Since I now use Win7 most of the time, I have AHCI enabled in BIOS.

Yesterday I needed to boot to WinXP so I disabled AHCI, booted XP. But when I finished I forget to enable AHCI. I booted Win7 and only realised my mistake when I saw the "Loading device drivers" window followed by "You need to reboot".

Have I messed up my Win7 installation ? It seems to be working OK as of now ( I enabled AHCI ).

Basically can Win7 installed with AHCI enabled be run with AHCI disabled ? And, of course, can Win7 installed with AHCI disabled be run with AHCI enabled ?
 
I dont think it matters if its ahci enabled or disabled... maybe the performance can improve a little bit with it enabled... not sure how much though... id guess like 1-3%
 
Not worried about performance. I remember reading, this was regarding XP, that if XP is installed with AHCI disabled and then run with it enabled, it messes up the installation and requires a re-install.
 
AnotherGuy said:
I dont think it matters if its ahci enabled or disabled... maybe the performance can improve a little bit with it enabled... not sure how much though... id guess like 1-3%
Click to expand...

Why are you pulling up numbers and making things up?

First off, performance isn't everything. Despite that, without AHCI, you have no Native Command Queuing and also do not, should you want it, have hotplugging.

Second off, yes it matters if you randomly enable it or disable it on an operating system - ESPECIALLY XP. XP will most likely blue screen on start up if you start in install in one and boot up in another.

If you want to change to AHCI after installation, you can do a registry modification in Windows XP and provide the appropriate drivers. Windows Vista and 7 should be able to identify the different controller without the need of reference drivers.

-Kevin
 
I'm going to try turning on AHCI with my Windows 7 rig, after installing the OS with it turned off. I know Vista and XP both freaked about this and refused to run. I want the hot-swappable feature with my ESATA drive. I'll let you know how it goes with my Intel 945 ICH8 chipset... I honestly don't expect it to work.

UPDATE: It didn't work. Windows 7 just rebooted same as Vista. However, I didn't give it another try, instead switched AHCI off and rebooted. On the next boot, Win7 asked me if I wanted to "launch repair" or start normally. I choose the second and it worked fine. I wonder if I left AHCI, went to the second boot if it would give me the option to launch repair, and if I did, would the drivers load? I'll try another time.

Good news, just like with Vista, it didn't appear to hose the system.
 
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SimMike2 said:
I'm going to try turning on AHCI with my Windows 7 rig, after installing the OS with it turned off. I know Vista and XP both freaked about this and refused to run. I want the hot-swappable feature with my ESATA drive. I'll let you know how it goes with my Intel 945 ICH8 chipset... I honestly don't expect it to work.

UPDATE: It didn't work. Windows 7 just rebooted same as Vista. However, I didn't give it another try, instead switched AHCI off and rebooted. On the next boot, Win7 asked me if I wanted to "launch repair" or start normally. I choose the second and it worked fine. I wonder if I left AHCI, went to the second boot if it would give me the option to launch repair, and if I did, would the drivers load? I'll try another time.

Good news, just like with Vista, it didn't appear to hose the system.
Click to expand...

Well the repair wont fix your system. I would imagine you need to make a registry modification to enable AHCI support before Vista or 7 will pick up the drivers.

-Kevin
 
So far my system is working fine, so I think it is safe to conclude that if Windows 7 is installed with AHCI enabled, but later run with it disabled, it's OK. At least with the 64-bit ultimate ver.
 
So far my system is working fine, so I think it is safe to conclude that if Windows 7 is installed with AHCI enabled, but later run with it disabled, it's OK. At least with the 64-bit ultimate ver.
 
So far my system is working fine, so I think it is safe to conclude that if Windows 7 is installed with AHCI enabled, but later run with it disabled, it's OK. At least with the 64-bit ultimate ver.
 
So far my system is working fine, so I think it is safe to conclude that if Windows 7 is installed with AHCI enabled, but later run with it disabled, it's OK. At least with the 64-bit ultimate ver.
 
You still have to do the registry change in Win7 to go from AHCI off to AHCI on after installing. I did it the other day and it worked fine.
 
I had to do the registry hack to move from AHCI to RAID when I had Vista x64. It was a pain finding the information through Google.
 
All I did was do this little registry setting with my Win7 64bit install, and AHCI now works. Not sure what driver it is using, but it appears to work fine, and now my ESATA drive can be turned on and used after Windows starts. Basically all I did was change the Start key listed below to 0. It was a 3. I could not get the Intel storage matrix drivers to install.

BTW, this is with a Win7 64 that was installed with IDE emulation of the SATA drives. Doing the below registry setting allowed me to switch to AHCI.

Vista 32/64 Windows7 32/64
- Run Regedit (from the command prompt)
- Navigate to "High Key Local Machine\System\CurrentControlSet\Services\msahci"
- edit the "Start" key and change the value from what it is to "0"
- this will tell Vista to check for AHCI on next boot and install the AHCI driver if it is in AHCI mode
- this installs the generic AHCI Microsoft driver and it is really a poor driver for your hardware and you will need the Intel ones to get full performance.

Hopefully the generic AHCI MS driver is not a "really poor driver" like the Vista driver.

UPDATE: I just went to the Intel site and downloaded the latest chipset inf files. Not sure if this installed the Intel AHCI driver, but now in my Device Manager, the AHCI controller is specifically the Intel one I have in my computer. I suspect it is the MS driver included in Windows 7, which was supplied by Intel.

Not sure if I am imagining this, but my computer seems a little snappier with my WD 640 blue drive. I was happy to see my Acronis boot disk sees the drives just fine with AHCI turned on. I'm happy.

Are all the features of AHCI turned on automatically?
 
Last edited:
SimMike2 said:
All I did was do this little registry setting with my Win7 64bit install, and AHCI now works. Not sure what driver it is using, but it appears to work fine, and now my ESATA drive can be turned on and used after Windows starts. Basically all I did was change the Start key listed below to 0. It was a 3. I could not get the Intel storage matrix drivers to install.

BTW, this is with a Win7 64 that was installed with IDE emulation of the SATA drives. Doing the below registry setting allowed me to switch to AHCI.

Vista 32/64 Windows7 32/64
- Run Regedit (from the command prompt)
- Navigate to "High Key Local Machine\System\CurrentControlSet\Services\msahci"
- edit the "Start" key and change the value from what it is to "0"
- this will tell Vista to check for AHCI on next boot and install the AHCI driver if it is in AHCI mode
- this installs the generic AHCI Microsoft driver and it is really a poor driver for your hardware and you will need the Intel ones to get full performance.

Hopefully the generic AHCI MS driver is not a "really poor driver" like the Vista driver.

UPDATE: I just went to the Intel site and downloaded the latest chipset inf files. Not sure if this installed the Intel AHCI driver, but now in my Device Manager, the AHCI controller is specifically the Intel one I have in my computer. I suspect it is the MS driver included in Windows 7, which was supplied by Intel.

Not sure if I am imagining this, but my computer seems a little snappier with my WD 640 blue drive. I was happy to see my Acronis boot disk sees the drives just fine with AHCI turned on. I'm happy.

Are all the features of AHCI turned on automatically?
Click to expand...

I believe the current Intel AHCI driver is only available installing the Intel matrix storage manager or loading the current Intel AHCI driver during the beginning of a custom Win install from a floppy or usb drive.
 
Gamingphreek said:
Why are you pulling up numbers and making things up?

First off, performance isn't everything. Despite that, without AHCI, you have no Native Command Queuing and also do not, should you want it, have hotplugging.

Second off, yes it matters if you randomly enable it or disable it on an operating system - ESPECIALLY XP. XP will most likely blue screen on start up if you start in install in one and boot up in another.

If you want to change to AHCI after installation, you can do a registry modification in Windows XP and provide the appropriate drivers. Windows Vista and 7 should be able to identify the different controller without the need of reference drivers.

-Kevin
Click to expand...

Yes I did make up the numbers... but referring to his post... my guess was right... it doesnt matter if its on or off once its installed with it on .... which was his case... it should still work.... AHCI features of course will be turned off... but that wasnt his question...

Thank you!
 
I can't get the Intel Storage Matrix drivers to load with my Win 7 64 bit install. Something about my hardware not meeting the minimum requirements, even though I have a core 2 duo running at 3.6 GHz, 4 GB of ram and everything else. The mainboard is a couple of years old. However, after running the Intel chipset inf updater, my Device Manager identifies the AHCI driver as Intel, not Microsoft.

Intel ICH8 SATA AHCI Controller -2824
Provider: Intel
Driver Date: 6/4/2009
Driver Version: 7.0.0.1013

It appears to be working perfectly fine with my two WD drives, one a blue and one a black drive. My ESATA drive, an older 250GB Maxtor also works fine in AHCI mode.
 
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AHCI supposedly has a big impact on AMD chipset/SATA performance.
Up to 40%.
Just search for AMD AHCI driver and you will a lot of posts of people having trouble with AMD/AHCI.
 
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