New GA-Z68XP-UD3 v1.3. I have 2 Seagate Barracuda 7200.12 drives plugged into the Intel Sata3 ports.
When I try to install Windows 7 x64, the installer tells me that one drive is "offline." That's a problem because it also won't let me install to the drives when I set them up as a RAID 1 volume.
There's nothing wrong with either drive. The BIOS (F8) sees them both. The Intel RAID software sees them and has no trouble with them. And when I connect only one and try to install, everything is good. I've tried each drive alone on the same SATA3 port and the same drive on each of the 2 SATA3 ports. All good. Only when 2 drives are plugged in does it tell me one is offline. And these are the only drives plugged in.
As for BIOS settings, I've tried many variations, including Optimized Default.
First time through, I updated the BIOS to F9d (Q-Flash), then set the BIOS to XHD. I then used the Intel RAID configurer and setup a RAID 1 volume. I then installed Windows 7 x64 without issues.
I installed the SSD Cache drive, got that running, everything was great. But then I decided to not use the beta BIOS and I flashed back to F8. That's all she wrote. The short story is that I ended up removing the SSD cache card and deleting the RAID 1 volume. That's when I discovered what I believe the whole problem is, the offline-ness.
I have tried flashing back to F9d but that didn't alter the behavior. I'm currently at F8, with Optimized Default settings.
I got it! After much more experimentation, I used DISKPART on both drives (on another system), cleaning and reformatting them. That worked. I have no idea why that made a difference since each drive was useable on it's own, but there it is. The drives are now set up as a RAID volume and windows installed flawlessly.
I hope this helps anyone else who stumbles across this bizarre problem.