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 Post subject: Enable AHCI
 Post Posted: Sat Aug 08, 2015 2:55 am 
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I was going through my BIOS looking at a few things and noticed that I never enabled AHCI for my SATA controller. Currently the controller is set to Native IDE.

For the best performance I should be using AHCI since all drives including my Blu-ray burner are SATA.

Of course, as expected, if I switch to AHCI now I will go into an endless boot loop. I THINK that I can fix this. Even if I toast it I just made an image of my SSD today and it is about a 9 minute restore to bring back both partitions.

I have two questions.

1) Will switching to AHCI improve performance over Native IDE to make the switch worthwhile?

2) Can anyone confirm that I'm looking at the right registry fix to resolve the endless reboot? Here is my proposed fix.

a. Open the registry key 'HKEY_LOCAL_MACHINE\System\CurrentControlSet\Services\Msahci'.

b. Set the value under 'Start' to '0'.

c. Delete the value 'StartOverride' if present.

d. Restart and enable AHCI in the BIOS. Also check the hard drive boot priority as it is likely to change.

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 Post subject: Re: Enable AHCI
 Post Posted: Sat Aug 08, 2015 3:22 am 
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Never mind... I gritted my teeth and went for it. :mrgreen: I'm going to leave the thread in case it might help someone else make the switch.

It worked like a charm with only one ill affect, I had to wipe my media library in Windows Media Player and let it re-index everything. I don't know why the change affected this but all my music was listed, just my play lists were gone. The play lists are already back.

At a glance everything else seems to be as it was. Sampling a few games, photos and trying my Excel spreadsheet that launches my videos all still worked fine.

The initial value for 'Start' under the key in the first post was 3. Changing to 0 seems to have totally done the trick in relation to switching to AHCI. I had no value or entry for 'StartOverride' but that is one of those entries that you may or may not have. I rather wish that I had the 'StartOverride' entry to delete so that I could have FULLY tested the fix. As is I have no reason to think other than it would be fine.

As an end result I can already see that things seem quicker. Part of this MAY be that I want it to be so but not all. I was experiencing quick disk access but it was like the SSD drive had to wake up, sort of like a mechanical drive that has shut down and has to spin up. Word and Excel 2007 along with Firefox were bad about this, all three are now near to instant.

Another favorable difference is that my post screen now reports the S.M.A.R.T. status of each of my drives. It is not a detailed report, just OK/BAD. I'm guessing on the 'BAD' part as all currently show OK. :mrgreen:


I should note that this fix was done within Windows 7 Ultimate. While it SHOULD work in Windows 8/8.1 I cannot say for fact. I have no idea as to Windows 10. LOL! I'll probably end up following up on both. ; )

OK, so I probably will not test this in Windows 10 as my laptop is already AHCI. I don't know that I want to mess with it, we shall see. Win 8/8.1 I can still test as I set up that drive on my media system while it was still 'Native IDE'. As soon as I remember to do so I'll boot with the Win 8 drive attached and see what happens. I REALLY do need to boot to that drive anyway as I haven't even upgraded it from 8 to 8.1 yet. I strongly suspect that I'll need to switch back to Native IDE in my BIOS for the Win 8 drive to properly boot.

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 Post subject: Re: Enable AHCI
 Post Posted: Sat Aug 08, 2015 1:38 pm 
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jaylach wrote:
2) Can anyone confirm that I'm looking at the right registry fix to resolve the endless reboot? Here is my proposed fix.

a. Open the registry key 'HKEY_LOCAL_MACHINE\System\CurrentControlSet\Services\Msahci'.

b. Set the value under 'Start' to '0'.

c. Delete the value 'StartOverride' if present.

d. Restart and enable AHCI in the BIOS. Also check the hard drive boot priority as it is likely to change.[/b]

Jay, i believe the information you're looking for is in the following MS article under "Let me fix it myself", or you could just run the "Fixit":

Error message occurs after you change the SATA mode of the boot drive:
https://support.microsoft.com/en-us/kb/922976


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 Post subject: Re: Enable AHCI
 Post Posted: Sat Aug 08, 2015 4:45 pm 
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I already did the a registry change to solve any issue in Win 7. I will still look at your link as the registry key I changed in 7 does not exist in 8.1.

Turns out that the registry change I made is the same as in the link. However it does give another key that may apply according to the system...
HKEY_LOCAL_MACHINE\System\CurrentControlSet\Services\IastorV

It would seem that the fix for Windows 8/8.1 is to boot normally in Native IDE or ATA SATA mode then set Windows to boot to Safe Mode via an elevated Command prompt with the following command.
Code:
bcdedit /set {current} safeboot minimal

Boot to the BIOS and change the SATA setting to AHCI and boot to Safe Mode.
Again via an elevated command prompt enter
Code:
bcdedit /deletevalue {current} safeboot

The system should now boot correctly to Windows 8/8.1.

I have not yet tried this but will let you know.


In either case all that is being done is to enable a driver for the different SATA mode. In Windows 7 it is done with a registry key and in 8.1 it is handled automatically by Safe Mode.

<edit> The command prompt did not work as expected. Win 8.1 did not load to Safe Mode. I MAY try making the boot change via EasyBCD to see what happens but I'm done for now. Making this switch for 8.1 is just playing anyway. Since the 8.1 drive is not normally even connected to the machine I can just as easily change the SATA mode in the BIOS when I do connect it. Also, since it is a raw install that isn't even updated, I could just install it with AHCI enabled. I'll play first though. :mrgreen:

One thing that AHCI allows that I didn't know is the hot swapping of SATA drives. Not that I'll use it but nice to know.

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