frozen on white screen with F20 bios (was working with F11) gigabyte X79

I has to get a RMA motherboard for my gigabyte X79 UD3. The new board came with bios F20. The machine had been functioning like a dream for the last 3 years. I am correct to assume that it is simply the bios that is causing this or is it another issue. I am unable to boot in safe mode. -x -v gave a result: "initiated unmount boot disk". Older bios are not available on their site. I will look around to see if it is available elsewhere. In the meantime, what do people think? Will the system simply not work with F20.

There were a bunch of disk checks before the system froze so I removed the boot disk and repaired it in an external dock. I am now no longer getting those disk checks but it still freezes.

i3930k
GTX670
x79 UD3

Thanks all

You can find older BIOS including F11 for this motherboard here.

Thanks, I was able to find it, but the bios doesn't allow me to downgrade. I tried stepping down from F20 to F16 and then F11 but it says that it is an "outdated bios". I am going to try a new clover install as that is supposed to be more stable and easier to update in the future. I am not holding my breath for that to work. I have looked into flashing to bios F11, but it seems like you need a running windows environment. It's annoying as I am going to lose my RAID array but I have a relatively recent backup so I should be fine. Any thoughts on my plan?