The unit usually has a letter “R” at the end of the product code indicating that this is the “refresh” version supporting Intel® Xeon® processor 5600 series.
As you noticed some of our 5600 series processors would require BIOS 45 as some other 5600 series would need BIOS 54.
You may also visit our Intel® Quality Document Management System which will provide information of the changes applied to your PBA.
You could reply to this thread with your PBA and I can look that up for you.
Thanks! My PBA is E22554-753. I found PCN 111309 - 01 which indicates that the board shipped with BIOS 60, so I guess that's not my issue. I guess I'll need to continue troubleshooting to figure out what's wrong.