Thank you Joseph, that did the trick! After studying the man page for mkinitrd, I also used --preload ahci to make sure the ahci driver was the first one to look for drives. My steps (for future reference): 1) Switch bios back to "legacy" sata mode 2) update modprobe.conf adding a scsi line for the ahci module 3) mkinitrd --preload ahci etc etc.. 4) reboot, switch bios to ahci mode 5) system booted just fine! -Gordon On Sat, Dec 20, 2008 at 11:35 AM, Joseph L. Casale <JCasale at activenetwerx.com> wrote: >>So I'm wondering what config files I need to tweak, to help the >>already installed system use the "new" ahci controller? Previously, >>it appears to have been using the piix module to access the drive with >>the root fs on it. > > So, you need modprobe.conf to reflect this as well as a new initrd. > On a similar system I have from Asus my modprobe.conf looks like this: > > alias scsi_hostadapter ata_piix > alias scsi_hostadapter1 ahci > > I assume the ata_piix is still required for the jmicron ide controller. > After editing this, run mkinitrd which will look there and then load the > required modules. > > HTH, > jlc > _______________________________________________ > CentOS mailing list > CentOS at centos.org > http://lists.centos.org/mailman/listinfo/centos >