Thinkpads Forum

i noticed if you installed windows already you need to change the registry to let AHCI run

and that you would not have to do this if you had set the BIOS to AHCI before you put in windows

so my question is, do both of the above situations end up with the same AHCI speed? or does the post-installation fix leave it a bit slower?

both end up with same speed.

AHCI mode is set in BIOS when the OS has drivers to run that way. Windows XP usually does not have drives so one has to put those later (that's what I did). Vista and W7 have those already built in.