[coreboot] Coreboot on asus KGPE-D16 - Black screen

[Ale]

Hello,
I have an Asus kgpe-d16 with 2 AMD opteron 6282 SE installed; obviously, since I had the first stock bios version the screen was black and no boot occurs because CPUs are not supported. So I have ordered a coreboot bios DIP and I have installed it but nothing has changed, same behaviour (only black screen and no sound, only fans starts). Can someone have some idea? I even try to log with the serial port but no log is shown at all...

P.S. Could it be that one of the CPUs is broken? Or that something went wrong during the flashing procedure over the DIP? Is there a way to check that the DIP is ok and with coreboot?
Thank you very much!