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Last reply by 08-24-2014 Unsolved
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Dell sets Win 7 BIOS to RAID - not AHCI - YOU CAN'T SWITCH

Believe it or not, many Dell PC's with Win 7 have their BIOS's pre-set to RAID ON rather than AHCI.  And you can't switch the setting in BIOS without getting a BSOD on the next boot.  The only SURE fix is to switch and re-install Win 7.

If you have ideas for a fix (without reinstalling) - please go to this other Dell thread and let us know  !!

MANY THANKS - hope to hear from you.

Replies (6)
10 Diamond

Hi glnz,

I'm not sure which model you re referring to but your statement is not entirely correct. Desktops with an SSD cache are set to RAID but most others are set to AHCI by default. And as you could learn if you did some searching, it's quite easy to switch from RAID to AHCI without reinstalling the OS. It would literally take me less time to change from RAID to AHCI than it took to write this message.

This is not a Dell issue. It's the same for any PC where there are RAID and AHCI options. And the same registry trick can fix the problem.

3 Argentum

Osprey - you're great and have helped on some past issues.

Oh - I wish you were 100% correct.

My Win 7 machine is Optiplex 780.  Never had an SSD - only a plain old regular HD.  Now that I'm thinking about adding a second HD, the RAID setting probably presents an issue.

Please do go to the other post above.  It talks about the most well-known MS KB article and its fix - that fix is not 100% complete in many instances.  And it was an odd Dell decision to start in RAID on so many of its Win 7 machines.

And I also tried Googling this issue, which is how I found the other Dell thread and the MS article and more. 

Your thoughts will be much appreciated, as always.

10 Diamond

You can add a second hard drive without setting up a array.

Of course, the Optiplex line is intended for business, so there's more of a tendency to use older standards. Some of these may not even have AHCI as an option.

10 Diamond

To setup an SSD you break the raid.  Turn off the Raid configuration Then Clone the drive. The other issue is Raid 0 or Raid 1 or Raid 5

Soft Raid 0 and Raid 5 are not recommended.  Raid 0 Mirroring is easy to clone to ssd.  You Break the mirror then turn off Raid and run the Microsoft patch.  Then shutdown and clone the 1 drive to an ssd.

Mirroring SSD's or Raid is not recommended for Raid.

If you want to keep your Raid and Add an SSD then you put a Controller in first.  Then add the SSD on a Apricorn velocity solo


Its relatively easy to change from RAID-ATA to RAID-AHCI on Vista / 7 / or 8 with the microsoft patch to prevent


However mixing and matching Raid 0 or Raid 5 is complicated.

INTEL RST Drivers Drop support for Earlier chipsets from version  9 to 10 to 11 to 12 to 13

AND 2TB is the limit for raid as the RST driver does not support larger volumes.

Single Drives larger than 2TB REQUIRE driver version 10.1 or higher.

And UEFI Secure Boot Cannot be switched to Legacy without a reinstall.

This is not Dell its Microsoft.


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3 Argentum

Osprey and speedstep - many thanks for such fast replies - and everyone knows you guys are phenomenal.

But the issue in the FIRST instance is that the MS KB article may not be complete.  And your post above speedstep is way beyond my needs or knowledge.

Please do re-read

and let us know there.  Thanks, gents !!

3 Argentum

Osprey and speedstep - after doing more research, I followed the MANUAL regedit instructions in the MS article you cited above (NOT the "fix-it" download), and so far seems to work.  My home Opti 780 is now booting into "RAID autodetect / AHCI".

The article is

QUESTION - Now that I have marked the two extra services to start at boot-up with AHCI, what would happen if I now set the BIOS to boot in ATA?  Would those extra services interfere with an old-style bootup?

I ask because I have a different Win 7 machine at work with its BIOS currently set to boot in ATA.  I am tempted to make the same changes as the MS article and switch the BIOS to AHCI.  But if I then get a BSOD in AHCI, would I be OK returning the BIOS to ATA, or am I now stuck with no way to set anything back because ATA doesn't like the two new services starting?


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