There's a new BIOS, probably beta since it's not been announced on the download pages...
ftp://ftp.asus.com.tw/pub/ASUS/mb/so...B/P5B-1405.zip

1. Update CPU ucode to support new processor
2. Revise SLP 2.0 rule
3. Enable hotplug support under AHCI mode
4. Fix displayed CPU frequency incorrectly after downgrade CPU ratio