I recently obtained an HP dc5750 Small Form Factor PC. This system includes in ATI SB600 Serial ATA controller. It also uses a BIOS named 786E3. With AHCI support compiled-in to Linux kernel 2.6.18, I would get errors to the tune of “device such-and-such failed to IDENTIFY”. I don’t remember the exact error message, and it’s fixed now; sorry. 😉
In my experience, all BIOSes before the v1.54A released on Nov. 9, 2006 come configured for Windows with the SATA controller stuck in a “Legacy IDE” mode. There isn’t even an option for regular operation. Once I upgraded to v1.54A, an option became available in BIOS for regular operation. After making this change in the BIOS, the drive worked beautifully with the AHCI SATA support in the Linux kernel.