Windows 7: AHCI : Enable in Windows 7 / Vista

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.

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.

@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

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.

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

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...

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.

@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

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).

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