Use this flash utility:
And wait for the 314.bin to arrive in the mail.
Ah yes, and there's this:
Since I still have no official status about this bios file I do not feel like putting it online anywhere due to legal problems. Those of you asking this bios do so on your own risk, it has been reported several times as working by now. I had one other which appeared to be broken but HP offered to swap that board no questions asked. I think they know the 3.13 bios is somewhat flakey to put it mildly.