ThinkPads and AHCI Hard Disks

I have a Thinkpad T60p and I wanted to upgrade to one of these new 7200 RPM 320G disks.  I purchased a Seagate Momentus drive and, as I’ve done with other disk upgrades, just plugged the drive into the laptop and launched my system restore DVD.

While the drive could be seen by the BIOS, the restore app couldn’t see it.  I tried a number of things, including hard wiring the disk to SATA 150, which the PC expects.  Unfortunately, nothing worked.

I eventually ran across a BIOS setting that set the hard drive controller into “compatibility mode”  I resisted this approach for a while as  typically compatibility == slow, but after looking into it I learned that compatibility mode simply meant that the controller disabled the AHCI mode in the drive.

What surprised me was that with a little research (Google is great if you know what you’re looking for) I found out that the install code for Windows XP (and my restore disks) didn’t understand ACHI disks.  So how did I get around this problem when I restored my system last year?

The answer was that the Hitachi disks that I’ve previously been faithful to (Hitachi purchased IBM’s DeskStar/TravelStar drive biz a few years ago) disabled ACHI mode by default so the BIOS setting didn’t matter for those drives. Now that I had a Seagate drive, I needed to make the mod in the BIOS.

Once I made the change things worked just fine.  I can re-enable the mode if necessary with an XP driver update but AHCI isn’t apparently necessary on a single user laptop, so I may keep things the way they are.

Live and learn.


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