I posted this incorrectly to the PowerPC forum, my apologies. I have a Early 2008 Mac Pro dual-quad 2.88GHz that failed to boot. Per the service manual I checked the diag leds and found 'errb' lit. I ordered new CPUs and replaced both of them. The 'errb' is STILL lit ?!? so back to the service manual and ordered a logic board. Replaced that and the 'errb' is STILL lit !?! I will replace the battery and next the power supply unless someone has experience and can share some sage wisdom before I chuck it all and build a PC.