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Windows 7: AHCI drive behavior

05 Apr 2011   #1
Shootist

Windows 7 Pro x64
 
 
AHCI drive behavior

The other day after reading about turning on AHCI after 7 is installed I did that.
After making the change in the registry and my BIOS and the system started back up, after another reboot from loading the drives for AHCI, I went into Disk Management and my drives, 3 of them, were listed in reverse order.

The drive that holds the OS partition (C), sys reserve part (No drive letter) and programs part (D) was listed as drive 2, IE the last drive in the system.
The last drive in the system, my G and F partitions, was listed as drive 0.
Is this normal behavior when enabling AHCI after the install of the OS? Does this happen if you enable AHCI before installing the OS?
Is it a BIOS thing?

Thanks.


My System SpecsSystem Spec
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05 Apr 2011   #2
GeneO

Windows 10 Pro. EFI boot partition, full EFI boot
 
 

Its a BIOS thing. Nothing guarantees the order of the drive number.
My System SpecsSystem Spec
05 Apr 2011   #3
Sardonicus

Windows 7 Home Premium 64 bit
 
 

You can sometimes fix the situation by changing the drive priority in the BIOS.

+1
It's a BIOS thing...nothing to do with AHCI.
My System SpecsSystem Spec
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05 Apr 2011   #4
Shootist

Windows 7 Pro x64
 
 

Well in the BIOS they are all seen in the correct order. SATA 1 (or 0) is my boot drive.
In the BOOT part of the BIOS Boot order SATA 1 is boot.
In BOOT part of BIOS Drive Order SATA 1 Seagate 250GB is drive 0.

When going back to IDE the order is correct in Disk management.

But then even when I boot to a Mustang PE USB stick the order is reversed when set to AHCI.
So I guess you guys are right. It a BIOS thing.

Thanks.
My System SpecsSystem Spec
05 Apr 2011   #5
TVeblen

Microsoft Community Contributor Award Recipient

Windows 7 64 Bit Home Premium SP1
 
 

What I did with my rig was (because you are in AHCI mode the drives are hot swappable) shut down, disconnect all but the boot drive, start up, get to the desktop then hot plug the SATA connector for my second drive. Check to be sure they were listed correctly in Disk Management, then restarted.

They stay in the correct order most of the time. On occasion I notice they've reversed again, but without intervention it goes back somehow.

I also made sure that Disk 0 was in SATA port #1 on the MB and Disk 1 was in port 2, even though I know that, according to science, this should not matter. What they hey - I'm OCD.

Bottom line is that with SATA and AHCI it just does not matter how the OS lists them.
My System SpecsSystem Spec
05 Apr 2011   #6
Shootist

Windows 7 Pro x64
 
 

Quote   Quote: Originally Posted by TVeblen View Post
What I did with my rig was (because you are in AHCI mode the drives are hot swappable) shut down, disconnect all but the boot drive, start up, get to the desktop then hot plug the SATA connector for my second drive. Check to be sure they were listed correctly in Disk Management, then restarted.

They stay in the correct order most of the time. On occasion I notice they've reversed again, but without intervention it goes back somehow.

I also made sure that Disk 0 was in SATA port #1 on the MB and Disk 1 was in port 2, even though I know that, according to science, this should not matter. What they hey - I'm OCD.

Bottom line is that with SATA and AHCI it just does not matter how the OS lists them.
Thanks for the tip. It worked. haven't rebooted yet to see if it sticks.

One other thing I noticed right away after building this new system was the drive I want as my E drive, C & D are partitions on the main drive (drive 0 on SATA port 1), ws connected to SATA port 2 but showed up in 7 as the third drive. The drive on SATA port 3 was listed as the second drive in the system.
My System SpecsSystem Spec
06 Apr 2011   #7
TVeblen

Microsoft Community Contributor Award Recipient

Windows 7 64 Bit Home Premium SP1
 
 

I am no software expert by any stretch of the imagination, but it makes sense to me that the OS queries the BIOS to get that drive info on startup. So it depends on the logic applied to the BIOS settings info and how that is translated to the OS and where and how the OS stores that info.

I bet someone here knows, but that is the extent of my programming curiosity!
My System SpecsSystem Spec
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 AHCI drive behavior




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