Using Xeon E5-26xx v2 CPUs in this server requires a BIOS update.
Updating using AFUDOS does not work (and will brick your server).
Requirements for update:
*) Server to upgrade
*) CH341A BIOS programmer
*) Hot air station
*) Soldering iron
*) New BIOS file.

First get the BIOS update file `B810Update.7z` linked to from this forum thread: https://forum.ixbt.com/topic.cgi?id=66:12091:13#13 .

Then open the server and use the hot air station to remove the BIOS flash chip.

When you have removed the chip solder it to the CH341A programmer:

Connect programmer to computer and install driver from CH341PAR.ZIP.
Run programmer software.

First it’s a good idea to read the existing data from the chip and save it, so that you have a backup in case the new bios doesn’t work on your specific server.
Then load the new bios file and write it to the chip.
After that you can solder the chip back in the server and try booting.