So yeah, cross flashing your 2008 Xserve to a 2008 Mac Pro with the proper ROM with the proper serial number apparently doesn’t work .

Now I have a 31 pound aluminum paperweight I don’t understand why the blank ROM worked fine but the one with my serial number and stuff on it didn’t it no longer detects the CPUs.

Someone suggested: “Try using a beta version of osx to see it that will help validate the serials and install to detect the cpus”

You have to be able to get it to post first… there’s now no way to communicate with the board other than getting a new board or reflashing the chip externally.