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guide ide ahci registry

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#1 +warwagon

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Posted 03 April 2011 - 04:47

About 2 months ago I installed an SSD drive in my media center. For some reason up until tonight I never checked what the Sata mode was set to in the bios. It was set to IDE. I also really wasn't keen in reinstalling windows. Of course once you change it in the bios from IDE to AHCI windows will no longer boot. So I looked around the internet and found some really great instruction to switch from IDE to AHCI without having to repair or reinstall windows.

You start with step 1 while you are still in windows in IDE mode.

1) Run the Registry Editor (regedit.exe)
2) Navigate to Registry Key: HKEY_LOCAL_MACHINE\System\CurrentControlSet\Services\Msahci
3) Set the "Start" value to 0 (zero)
4) Navigate to Registry Key: HKEY_LOCAL_MACHINE\System\CurrentControlSet\Services\Pciide
5) Set the "Start" value to 0 (zero)
6) Shut down
7) Start up again, but before Windows boots go into the BIOS configuration screens and change the disk mode to "AHCI". Save the new BIOS configuration and restart so that Windows boots.

When Windows starts, it will detect the change, load new disk drivers, and do one more reboot to start up with them.


#2 The Laughing Man

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Posted 03 April 2011 - 04:59

I had done this not more than 5 days ago with my new rig. Installed Windows 7 and forgot to change the setting , Just a simple search helped. I can confirm this method works !

#3 ironsight2000

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Posted 03 April 2011 - 05:16

mine freezes at post

#4 OP +warwagon

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Posted 03 April 2011 - 05:21

mine freezes at post


You've got other problems than windows.

#5 ironsight2000

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Posted 03 April 2011 - 05:22

I got back up but had to go back to IDE

#6 humble3d

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Posted 08 April 2011 - 10:50

Thank you very much... I was really stumped... :)

#7 -T-

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Posted 08 April 2011 - 11:19

I did it in my BIOS didn't need to change anything in Windows. Is my install stupified?

#8 Shaun N.

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Posted 08 April 2011 - 11:22

Mine meows at me on startup?

#9 neo158

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Posted 08 April 2011 - 20:30

I had to do this with my install as the new mobo had AHCI enabled by default.

Also, this trick only works on Windows Vista/7.

Microsoft have a Fix-It for this, it's linked in my sig.

#10 OP +warwagon

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Posted 09 April 2011 - 02:33

I had to do this with my install as the new mobo had AHCI enabled by default.

Also, this trick only works on Windows Vista/7.

Microsoft have a Fix-It for this, it's linked in my sig.


Thanks for the head up. Title edited

#11 Draconian Guppy

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Posted 11 April 2011 - 20:47

Is there any real world benefit for using AHCI instead of IDE if i'm not running raid?

#12 OP +warwagon

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Posted 11 April 2011 - 21:05

Is there any real world benefit for using AHCI instead of IDE if i'm not running raid?


Apparently AHCI gives you much better performance when using SSD drives (but don't quote me on that)

#13 Draconian Guppy

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Posted 11 April 2011 - 21:11

checked neo158's sig and came up with:


AHCI provides several features for SATA devices. These include hot plug functionality and power management functionality. For more information about the AHCI specification, visit the following Intel Web site:

http://www.intel.com...ialata/ahci.htm

No really worth it I guess, at least not for HDDs not paired in any raid.

#14 Nagisan

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Posted 11 April 2011 - 21:14

Msahci is already set to 3 and pciide is already set to 0, I assume this is running in AHCI mode already, right?

#15 Raa

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Posted 11 April 2011 - 23:19

Always use AHCI if possible.
Been doing a similar method to this for XP computers for years.