I just got a new Gigabyte GA-P55A-UD4P motherboard, and I am trying to get Windows 7 64-bit to recognize an external hard drive connected to the eSATA ports.
I've set the the following BIOS options:
PCH SATA Control Mode to AHCI
HPET Mode to 64-bit
eSATA Controller Enabled
eSATA Ctrl Mode to AHCI
GSATA Controller Enabled
GSATA Ctrl Mode to AHCI
When I first connected drive the motherboard, a tray icon said that I needed to install a driver to get the hard drive to be recognized. So I went to the device manager, and under other devices there was a device titled JMicron something (sadly, I don't remember exactly what it was titled). So I placed the driver disc in the optical driver, and I had the missing device search for the driver on the driver disc. The device manager found the driver, and new device came up as JMicron SATA something (again, I don't exactly remember what it was titled). So I restarted, then I powered on my external hard drive, but Windows still didn't recognize it. If I try turning on the external drive before I boot-up my system the drive still isn't being recognized by Windows.
The drive does get recognized by the BIOS on start-up if I power on the external drive before I boot-up my system. So that tells me that the BIOS is detecting it correctly; and the problems is with Windows.