AHCI and SSDs

Art · 18 Nov 2009 at 20:46

So I've just got myself a Kingston V+ 64GB SSD and I've spent my spare time in the last few days getting it installed, optimised, etc. with a fresh W7 Pro install.

Having got everything settled in though I noticed I've managed to miss setting my machine to AHCI mode. D'oh!

A little Googling says you can't just switch it on restrospectively (and I do indeed get BSODs if I try that), but that there's a pretty complicated hack to do it once you've installed Windows. Or, a fresh install fixes it. I don't really want to fresh reinstall so I'm wondering if imaging could help here: does Windows have to actually be installed on the drive when its in AHCI mode to work with it, or can I image my C: drive, format the partition, switch it to AHCI and then restore the image? Any ideas?

If not and I can't be bothered to reinstall, will being in IDE mode actually do any damage? I know there's a performance drop and SATA drives won't be hot-swappable but I'm wondering if it causes anything else.

Venares · 18 Nov 2009 at 20:56

Still would not work as your Windows image would still be using the IDE drivers.
Only way is to change the registry.

HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\services\msahci

Change "Start" to 0 (ZERO)

Easy peasy realy

broona · 18 Nov 2009 at 21:01

You only need to change one registry setting, I just did it last week on a Windows 7 system, change msahci from 3 to 0 - http://support.microsoft.com/kb/922976

Art · 18 Nov 2009 at 21:15

broona said:
You only need to change one registry setting, I just did it last week on a Windows 7 system, change msahci from 3 to 0 - http://support.microsoft.com/kb/922976

Really? Obviously my Google-Fu sucks then, all I found were reports of people mucking about with .bat files or reinstalling.

Awesome, thanks for that. I'll try it when I next get the chance. I'm stuck in a lab at the moment and I'm itching to play around with my new drive. :rolleyes:

thebandit · 18 Nov 2009 at 21:45

I must be behind the times, I thought AHCI on SSD's was not ideal ?

Art · 18 Nov 2009 at 21:50

thebandit said:
I must be behind the times, I thought AHCI on SSD's was not ideal ?

The options are AHCI, IDE or RAID. Obviously you can't use RAID if you've only one drive. IDE is the old method of accessing data on a hard drive. AHCI is a more modern version designed with SATA drives in mind. So given the options, AHCI seems to be best.

Xelene · 18 Nov 2009 at 23:10

Art said:
The options are AHCI, IDE or RAID. Obviously you can't use RAID if you've only one drive. IDE is the old method of accessing data on a hard drive. AHCI is a more modern version designed with SATA drives in mind. So given the options, AHCI seems to be best.

Windows 7 won't automagically tweak your SSD if you install in AHCI mode, but the performance is lower in IDE. I installed in IDE then registry tweaked it to AHCI.

Art · 18 Nov 2009 at 23:20

sldsmkd said:
Windows 7 won't automagically tweak your SSD if you install in AHCI mode, but the performance is lower in IDE. I installed in IDE then registry tweaked it to AHCI.

Didn't know that either. Had mine installed in IDE but I want to use AHCI for a hot swappable SATA drive I have anyway.

Does W7 *always* tweak the setting for SSDs in IDE mode? I don't think mine did.