Disabling AHCI BSOD

BizSAR · May 22, 2008

Hello!

I have what seems to be a rare issue since I can't find any help on the subject.

I installed Vista Ultimate 64-bit with AHCI successfully. Now, I would like to disable AHCI and revert back to eIDE. When I make that change in the BIOS, I get the 0x0000007B BSOD until I reset the BIOS back to AHCI support. Just the opposite of the issues I'm seeing other people reporting.

When I run a Vista repair, it reports everything as functional.

All of the information I can find discusses enabling AHCI, not the other way around.
I'm running an ASUS P5KE-WiFi AP mobo utilizing the latest BIOS.

Any thoughts?

dmex · May 22, 2008

Hi Bizsar,

When you install Vista using AHCI mode you can not change it without reinstalling Vista again.

Steven

BizSAR · May 22, 2008

Thank you very much for the reply.

Respectfully, I simply cannot believe that I have to reinstall, when there is a MS KB article that explains a workaround for the exact opposite problem when the exact BSOD occurs. If I don't have to reinstall to enable AHCI, why would I need to reinstall if I wish to disable AHCI?

As you may know, and as explained in the KB article, the issue that causes the 0x7B BSOD is that the AHCI driver in Vista is disabled, and the KB article goes on to describe enabling the driver in the registry. It seems to me the inverse is happening here: The eIDE driver has been disabled, and it seems simply finding the correct registry key and enabling it would do the trick. The issue at hand, therefore, is finding the correct registry key/subkey. Is this oversimplification of the issue?

I find it very odd that this has not come up before, especially since so many people (like myself) mistakenly believe that AHCI is going to improve HD performance on a basic system that isn't being used in a server capacity, especially on a gaming system, and wish to disable AHCI to improve HD performance for sequential access applications (like games).

UPDATE: It looks like the two drivers that need to be enabled just might be pciide and intelide...

dmex · May 22, 2008

Hey Bizsar,

There might be a way to enable the drivers after installing in AHCI mode Im just not sure..., the only problem I can see stoping you is Vista didnt load anything with IDE support since AHCI superceeds the IDE specifications and even conflicts with it hence the difference in mode settings...

Keep us updated, I will let you know if I find anything...
Steven

Chappy · May 23, 2008

Well, while there is a definite possibility that certain IDE support files need to be installed still, the MSKB article you linked has you change the key value to "0" to enable AHCI. When the value is 0 to enable, the opposite value is "1" to disable so you could try that for starters.

This bit from the MSKB article makes me believe that the IDE drivers were NOT installed during your Vista installation since you chose the AHCI option...just as Steven pointed out above

MSKB Article said:
During the Windows Vista installation process, any unused storage drivers are disabled. This behavior speeds up the operating system's startup process. When you change the boot drive to a driver that has been disabled, you must enable the new driver before you change the hardware configuration.

If you can find all the proper files and register anything needed with Windows services to enable IDE, it's possible that you may not have to reinstall Vista, however..I think if you do a Repair Install and enable IDE during that, you can get this al back and save your data and installation.

BizSAR · May 28, 2008

Well, I messed around with it some more, and failed. So I did just reinstall.

I'll work at it some more and post my findings later.

Thanks for all your help.

Dospac · May 29, 2008

I'm curious about this as well. I installed Vista64 w/AHCI enabled and my HD performance has been great. Unfortunately the disappearing DVD drive of doom pissed me off so much I've enabled the jmicron IDE controller and hooked up an old DVD-ROM drive instead of the sata drive I was using before.

Long story short, I can either re-install w/AHCI disabled or buy a better IDE DVD-RW drive and just use that. :D

wufawutian · Jun 2, 2008

BizSAR said:
Well, I messed around with it some more, and failed. So I did just reinstall.

I'll work at it some more and post my findings later.

Thanks for all your help.

Dear BizSAR：
since you both using ACHI and IDE , could you psot the performance differemce between ACHI and IDE ( same harddisk) ? I just wonder the result, I also heard from many people they said ACHI open will improve the performance , but I not sure

dmex · Jun 2, 2008

wufawutian said:
BizSAR said:

Well, I messed around with it some more, and failed. So I did just reinstall.

I'll work at it some more and post my findings later.

Thanks for all your help.

Click to expand...

Dear BizSAR：
since you both using ACHI and IDE , could you psot the performance differemce between ACHI and IDE ( same harddisk) ? I just wonder the result, I also heard from many people they said ACHI open will improve the performance , but I not sure

AHCI is bad for games and playing music because its not good with synchronised read/writes, Its only good for file servers... IDE gets way better performance.

WildEagle · Jun 3, 2008

dmex said:
Hi Bizsar,

When you install Vista using AHCI mode you can not change it without reinstalling Vista again.

Steven

That's not true. All that needs to be done, is the registry edit of setting in the registry as in the below instructions to 1, instead of zero, reboot, then disable AHCI mode in the bios. I've done this many times and it works.

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.

Note number 6, as in the instructions above, which came from Microsoft, that the Value in the registry entry showen in Number 4, must be set to 1. Then reboot, go in to the bios disable AHCI mode, then boot back in to Windows Vista, and Windows Vista will install the IDE driver, and redetect any harddrives in the system.

However if the person has used the Intel Matrix Storage driver for the AHCI driver, that the user most likely will not be able to uninstall the Intel Matrix Storage driver.

dmex · Jun 3, 2008

WildEagle said:
That's not true. All that needs to be done, is the registry edit of setting in the registry as in the below instructions to 1, instead of zero, reboot, then disable AHCI mode in the bios. I've done this many times and it works.

Last time I checked for a method there wasn't information about a successful way of disabling AHCI mode after installing Vista.

Does this work if you had enabled AHCI then installed Vista before switching back it IDE mode or only after installing using IDE then switching to AHCI and wanting to swtch back later?

Steven

WildEagle · Jun 3, 2008

Yes, this works for me if I install in AHCI and then switch to IDE mode, or going from IDE mode to AHCI, and then back to AHCI.

dmex · Jun 3, 2008

WildEagle said:
Yes, this works for me if I install in AHCI and then switch to IDE mode, or going from IDE mode to AHCI, and then back to AHCI.

Cheers WildEagle, Thats some useful information, Did you want to make a Tutorial for anyone who would need a procedure for re-enabling IDE?

WildEagle · Jun 4, 2008

I'll make one. Might be a little while, got my head stuck in Mass Effect on the PC.

BizSAR · Jun 4, 2008

dmex said:
WildEagle said:

Yes, this works for me if I install in AHCI and then switch to IDE mode, or going from IDE mode to AHCI, and then back to AHCI.

Click to expand...

Cheers WildEagle, Thats some useful information, Did you want to make a Tutorial for anyone who would need a procedure for re-enabling IDE?

That is fantastic, even though it's a lot simpler than I would have thought (simply reversing MS' own directions for switching to AHCI). I can safely tell you that those are the only instructions for switching back from AHCI on the 'net. I searched through countless numbers of Google searches.

wufawutian: unfortunately I didn't benchmark my HD with AHCI enabled, so I don't really have data to compare to my current setup. That's something else I can't find: gaming benchmark comparisons between AHCI and e-IDE.

Dospac · Jun 4, 2008

Hah.. So I installed the Intel Matrix driver. Not possible to go back to IDE emulated mode at all now? doh =[

BizSAR · Jun 4, 2008

Have you tried it anyway?

Dospac · Jun 4, 2008

I haven't had a chance to hook up the sata dvd-rw again. Been super busy w/work lately. Will try it soon though and see if the Intel driver fixed the disappearing drive problem. Then I'll really worry about uninstalling the thing..

Chappy · Jun 4, 2008

dmex said:
WildEagle said:

Yes, this works for me if I install in AHCI and then switch to IDE mode, or going from IDE mode to AHCI, and then back to AHCI.

Click to expand...

Cheers WildEagle, Thats some useful information, Did you want to make a Tutorial for anyone who would need a procedure for re-enabling IDE?

Hmmm...I thought I mentioned that a little earlier in the post...guess nobody saw it eh

Chappy said:
the MSKB article you linked has you change the key value to "0" to enable AHCI. When the value is 0 to enable, the opposite value is "1" to disable so you could try that for starters.

Singtoh · Jul 13, 2008

I have recently enabled AHCI with exactly the same reference, My machine, 64 bit Ultimate T-61 was running in compatability mode. I went to the registry to enable it there, and my value was a 4(for some reason unknown), which I changed to a 0 to enable it like the article suggests. Just thought I would add this!

Cheers,

Singtoh

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