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

 

[Night Hawk]

You would need to look in the bios settings for hard drives. The option for Raid as well as ide mode and AHCI would be found in the Integrated Periperals section.

As for your finding on drivers there that shows you have the necessary drivers already installed. That should out the need for any worry about getting drivers on when switching modes.

Here the board came already set to the AHCI mode from the factory but 7 was dragging. I then switched it to the Native ide mode until lately seeing the clean install go on.

The initial install however was to one of the sata 3 not sata II drives when getting the case together. Apparently the S3 controller is a bit more fussy.

 

[ICIT2LOL]

Hum Night Hawk all I have is what the HDD brand is in Main there is nothing to do with HDD's in Advanced and then it just goes onto Display Security Boot and Exit - it seems a very simplistic BIOS to me.

Anyway it is running a light speed faster than the old Vista did witha WEI of 4.5 so no real worries.

All the drivers are up to scratch so am not that concerned and I am certain the owner will be pleased with the end result.

Thanks for the tips though I shall keep those in mind (whats left of it LOL!!)

 

[Night Hawk]

Sometimes the options are hidden from view depending on which bios program is being used. Here it would be Award on the Gigabyte model board.

When pressing enter on the hard drives item you might find a sub menu for settings there likely if at all under Boot. Is this on a laptop or desktop by the way? Generally laptops will tend to see the limited bios options.

 

[ICIT2LOL]

Thanks Night Hawk yeah my friend this one is a Phoenix BIOS and it doesn't let you "land" on th HDD - it is a very very basic BIOS from what I am used to.

 

[Night Hawk]

Ouch! That's a tuff break for you alright!

 

[ICIT2LOL]

No probs mate I suppose after all is said and done it is running faster than that dog Vista she had on it.

 

[pknight]

I have skimmed through this entire thread over the past couple of days, and I just want to get some opinions before I move forward.

I am going to put an SSD in my Dell desktop, and move the OS and programs to it. My question has to do with the need to enable AHCI.

The BIOS options that I have include "RAID on every bootup" (currently selected) and "RAID if signed drives, otherwise AHCI." ("Signed" is apparently Dell-speak for a drive being assigned to a RAID configuration.) I have two SATA HDDs in the system, but they are not configured in a RAID.

Several people in this thread have said that if you are currently configured as RAID, even if you have no HDDs in a RAID (which describes my system), you are effectively already using AHCI, and have nothing to gain by enabling AHCI. Is this the case even for SSDs?

Thanks for any and all input.

 

[Night Hawk]

AHCI is basically SCSI mode. The old term there was used for faster means of storage back in the 90s when you would more often hear the term SCSI array since companies were looking for faster access to data stored on network and other drives.

Switching to the AHCI mode sees Windows mount the volumes on the drives a little bit differently. You see that during the post screens when no factory logo screen is enabled where an extra screen appears to list the drives presently in the AHCI mode as SCSI devices.

With an SSD the technology is what is different there being similar in nature to a usb flash drive only seeing larger capacities for most unless you grab an expensive flash drive! Boot time is the preference there over the faster access time seen when in the AHCI mode.

As for RAID mainly that is best applied to server applications rather then your main OS drive. There are also various types of RAID and arrays as well such as either mirrored or even taking a single volume and spanning it across several drives to increase the total capacity.

 

[pknight]

Thank you Night Hawk. My question was more about whether I needed to activate AHCI when installing a SSD if the controller is configured as RAID. Some here have said that if the controller is configured as RAID, AHCI is activated and there is no need to change the controller configuration.

 

[Night Hawk]

One thing I found here was when the board has an ide or Native ide mode depending on who made it and it comes set to AHCI by default you can run into problems with any fresh install of 7. The board here came set to AHCI by default and when the initial install of 7 went on it seemed to be taking far too long for Windows to load up.

When switching over to the Native ide mode suddenly 7 was starting right up as it should in pronto time! Apparently something was lacking and more recently when in need of another clean install of 7 I waited this time until all drivers were on along with everything and then simply switched modes.

The results were instantly requiring a restart to finish the install Windows perform as mentioned earlier in the guide here. Likewise I suspect the SSD install may also run into some problems setting it to AHCI too soon before you have all the board drivers on at least which would include the sata/Raid controller as well as ide controller drivers necessary.

There's a big difference between RAID and AHCI to know however. For a start Raid is what it is pairing up drives if not adding more into an array. AHCI on the other hand is a particular drive mode where any volume is mounted as a logical drive with a slight difference to boost access times.

To understand that better a good write up on SCSI can be looked over at SCSI and RAID hard drives

 

[pknight]

When I set bios to raid and boot into my ssd os my hdd raid0 shows up as drive f and I can access the files on it. Which is what I want. I was wondering if I am getting ahci for my ssd? I read on forums that with raid enabled I get ahci eneabled for ssd. Is this true and if so do I get trim? It is a ocz vertex2 120gig

Newer computers and newer controllers typically only have IDE and RAID. If you select RAID and do NOT create a RAID all drives are running in AHCI. -WS

This is one of the messages I was referring to (#289 in this thread).

What makes me wonder about this is that my controller has a RAID option (the default, to which it is currently set) and an option to use RAID if the HDDs are assigned to a RAID and AHCI if they are not. If WindowsStar is correct, there would seem to be no difference between these two options. If my current drives were configured as a RAID right now, the default setting on my controller would manage the RAID. According to WindowsStar, since my drives are NOT configured as a RAID, they should be running in AHCI. This is exactly how the controller option that I am NOT using is supposed to work. So, how are these option different, given what WindowsStar has said?

Also, when I look at the Registry option that needs to be changed to enable AHCI, it is currently zero. Does that have to be 3 in order for AHCI to operate, or does changing it just allow you to change the BIOS options?

I want to be sure that I have the benefits of AHCI for my SSD, but if I don't need to change the registry and BIOS, I would rather not.

FWIW, there is no IDE controller on this machine. Only a RAID controller.

EDIT:
OK. I see that I had the registry values reversed. If the msahci value is 0, then it is set for AHCI. So, apparently AHCI is activated without my having to do anything. However, I am still confused by the apparently redundant controller option in my BIOS, but I can live with being confused.

Thanks again.

 

[pknight]

I BSOD'd upon boot after this. Right as the orbs for the Windows Loading Screen showed up, quick blip of a blue screen and restarted by itself.

Had to boot into my 'last known good configuration'.

OK. On to the next machine. On another computer, configured essentially like the one I discussed above (same controller, one internal SATA HDD not assigned to RAID, BIOS set for RAID), I followed the tutorial (changed registry entry, changed BIOS to the option to autodetect RAID/AHCI, which should use AHCI since I have no RAID), but when the system rebooted after the BIOS change, I experienced what DarkNovaGamer described above (way back when this thread was started), except that after the blue screen blip (about .1 sec), I get a "failed to boot" message. I have to go back into the BIOS to select RAID to get it to boot again.

The conversation when DNG had the problem centered on his motherboard not allowing a switch from IDE to SATA. However, the only controller in these machines I am dealing with is SATA, so that is not the issue.

Which brings me back to my original question, which was for advice on the veracity of statements that if your controller is configured for RAID, you already have AHCI, and should not have to do anything. A couple of folks here stated this a few years back, but others have gone out of their way to discuss the differences between RAID and AHCI. I have no interest in RAID per se, I just want to have the benefits of AHCI for when I install SSDs. If I already have these benefits, then fine. If not, I need to figure out why this machine will not boot up after selecting AHCI in the BIOS.

 

[WindowsStar]

@pknight

I work with a lot of Dell computers, you can leave it set to RAID. When there is NO RAID setup it picks AHCI automatically, no need to pick AHCI in the BIOS. -WS

 

[pknight]

Thanks. I got the SSD working, but am having problems getting a junction to my old Users folder working. I have posted about that elsewhere. Thanks again.

 

[calpeters]

I'm having issues doing this... I went in and changed the registry key as instructed. But when you then restart and change the BIOS to AHCI, the computer won't boot at all, saying "boot sector not found" and you CAN'T get into windows to "finish" the driver installation. But when you go back and check the registry key is still says "0", but device manager still looks like this.....

....which say's I'm still using IDE. How can I get the machine to boot after I switch to AHCI in the BIOS???

Thanks for any help!!

Cal

 

[calpeters]

never mind....I tried F8 after switching to AHCI in the BIOS, and selected the hard drive and it booted right up with the "generic" driver, then I updated it with the AMD driver. All is well...

 

[Win7x]

Extra information!

Only changing msachi to 0 in registry isn't enough if you want best outcome when using AHCI after installing Windows in IDE mode. It will work but isn't most optimal
to use with AHCI mode. If you do it this way boot will take longer than with optimal
settings in AHCI mode. This is because IDE controllers still load themselves when Windows boot, they are not used and are useless at this point, you should choose disable or use only when necessary(won't be necessary in AHCI), default in device manager hidden devices is to load them when Windows boot, disabling them or choosing use only when necessary will make boot in AHCI mode much faster. You should go to device manager -> show hidden devices -> choose pciide -> choose disable or only when necessary option and also do this to IDE channel and Intel(or whatever manufacturer you have) ide. Then reboot and notice faster boot because IDE controllers aren't loaded when Windows start.

 

[WindowsStar]

@Win7x

While this was extremely true in Windows XP this is not much of a concern in Windows 7. Windows 7 is very good about disabling what is not needed automatically (especially low level drivers); hence the issues here where AHCI is off when adding a drive that uses AHCI. -WS

 

[Win7x]

It doesn't always disable them automatically in Windows 7. At least when I changed my AHCI registry setting to 0 it did delete ata channels and other IDE related devices in device manager but showed IDE channel, pciide and Intel IDE in hidden devices which were set to start automatically when Windows start. It is good to check those in hidden devices. Yes it does delete IDE controllers that are not in hidden devices, but not always disable those that are in hidden devices(pciide, Intel IDE, IDE channel).

 

[tweakradje]

I have been doing this trick this week with windows seven and intel ich8 controller.

It is NOT so easy as described in the O.P. The situation was like this.

The BIOS was configured for RAID0, that uses the iaStorV (mind the V in that!) service and device driver.
Windows 7 was installed using this driver. Then we wanted to switch back to AHCI.
Doing that only in the BIOS causes the well known BSOD. Why? There was a simple answer for that (after spending some time figuring it out)

When switching the mode in the BIOS the board switches to a different device, so a different pnp DEV_ID. Windows never liked that on the main storage level. Always BSOD.

step one: you need to know the pnp id for the new storage controller. In my case it was PCI\VEN_8086&DEV_1C03&CC_0106. This is both supported by the builtin Microsoft AHCI driver, but also by the intel iaStor service/device driver (mind it is without the V here!)

Also you need to know the class id (is in the msahci.inf or iaStorAHCI.inf file)
This is in this case {4d36e96a-e325-11ce-bfc1-08002be10318} which is the "IDE ATA/ATAPI controllers" class.

You can check HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Control\Class\{4D36E96A-E325-11CE-BFC1-08002BE10318}

Now you can get it to work.

This one is so critical. When not done properly you get BSOD.
Open the registry and goto HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Control\CriticalDeviceDatabase

Now create a new KEY with the proper pnp id in this format pci#ven_8086&dev_1c03&cc_0106
Add this STRING value called ClassGUID with {4D36E96A-E325-11CE-BFC1-08002BE10318}

Make sure that the AHCI service is started during boot time. Goto HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\services\msahci and set Start to 0 (at boot time)

Now reboot and go into the BIOS to switch the controller mode from whatever to AHCI.
Save your BIOS settings and reboot.

Now the AHCI driver will find the new controller and asks you to reboot again. If you have an intel controller I advise you to install the iaStor driver at this point (you must download it at the intel download center)
Go into device management now and find the new controller at the "IDE ATA/ATAPI controllers" (familiar name?)
Now right click the controller and select "Update Driver Software...". Point to the unpacked iaStor driver you downloaded. Now reboot when asked.

After successfully installing the iaStor driver (it has little better performance) you can set the ahci service back to "on demand"
Start regedit again. Goto HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\services\msahci and set Start to 3 (on demand)

You might want to do some housekeeping in you hardware tree now. Open a DOS box with cmd.exe and type:
set devmgr_show_nonpresent_devices=1
compmgmt.msc
Now goto Device Manager and in the menu View choose Show hidden devices.
Walk the hardware tree and search for grey devices. You can delete them.

Cheers