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Mac Pro 2006 CPU B fail

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I bought an as-is original 2006 Mac Pro that I'm trying to get working. Unfortunately, I know nothing about its history. As found it was complete except for the RAM, video card, hard drive, and side cover. I bought a pair of 1GB Samsung 667MHz FB DDR2 DIMMs, and flashed a Radion HD3870 with Mac firmware.


It turns on, but there is no turn on chime, and the sleep LED remains on, then after about 5 seconds, the CPU B fail LED turns on. I have tired swapping the CPUs, and running it with only one CPU in both the A and B sockets with no change. The sleep LED blinks if I turn it on with no RAM, so at least it can detect a RAM error. It doesn't appear to detect the keyboard and mouse, so I can't reset the pram, but I did remove the battery. I also tried it without the video card in case my flashed 3870 is causing problems, but there's still no chime. I even tried the firmware recovery procedure, but the sleep light just blinks rapidly when I hold the power button and it never opens the DVD dive.


Everything is pointing to a bad logic board, but before I call it dead, is there anything else I'm missing? Does the Mac pro logic board have any known weaknesses or common failures?

As a last ditch effort, I tried pulling the firmware chip and reprogramming it in an EPROM programmer using the file from the emergency firmware recovery CD. The contents of the firmware chip closely matched what was in the file although the file had a few small things missing (like the serial number, as you would expect). The computer's behavior is exactly the same, so I have to assume it's not caused by corrupted firmware. It was a long shot anyway.


One piece of information to add is that if I only have CPU A installed, I get the CPUA FAIL light. If both CPUs, or only CPU B is installed, CPUB FAIL lights up.


Apart from some damage to the case, it looks like new. The fans and heat sinks are spotless, so I'm guessing it was the victim of an unfortunate accident when it was new(zapped by static, power surge, someone dropped a screw in while it was running,...). Without knowing something about what was done to it, I don't know where else to look, so I guess it's a parts machine unless I find a cheap logic board.

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