It seems you have an old revision of the board (R1.1), while the new BIOS was released for another revision of the board (R2.1). You need that new BIOS to have support for 56xx, a simple microcode won't do it. Try to flash again with the default settings in BIOS. If the flashing still fails, use the "CPU Patch" tab in MMTool to extract and insert the needed microcodes. But you still won't see the 56xx CPUs working.

Bios R 2.1 Extract microcode
Insert in R 1.1 (rev 1.2) CPU-ID 06A5, 06C0, 06C1
CPU 56** not work.
if add 06C2, 06F2 This is not a valid CPU MicroCode Patch file.

any idea ?
Thnaks!