Hello, I have a early 2009 Mac Pro 4,1. Out of no where while using it just shut it off completely and when I went to go reboot it, everything sounded fine except that I didn't hear the start up chime and my display remained inactive. The light above the power button stays solid and when I press the power button while holding DIAG button and watching the status lights, the EFI DONE and GPU OK Led's light up for a second but do not stay lit up. But the PSUPWR OK led stays lit up green. I've gone through the Technicians support document and have done everything I could for trouble shooting. I've removed everything and tested with DIAG button after each time I added back a peace of hardware. After doing that with no errors I took out the Coin cell battery and disconnected the PSU from the wall and let it sit for 24 hours as recommended to reset the SMC and after that I tried powering it on, same thing and no changes in how it responds. I've also tried to do a PRAM reset and that doesn't work because it doesn't boot far enough to do so. No chime, no display nothing. I have taken out the hard drives and tested them via USB adapter on my Macbook pro and they all showed up fine, And I tried the Nivida Geforce 120 in another desktop computer and it worked fine. I am not getting any error or temperature issue status lights anywhere on the processor try or Main logic board. ""NOTE: All fan's, and HDD's spin up and sound as they normally would after pressing the power button."" ""NOTE: After powering it on and having everything spin up (fans and HDD's) and waiting a few minutes I press the power button once to turn it off and it goes off instantly"" ""NOTE: I've reseated all of the ram modules, processor tray and all connectors on the main logic board (All power and normal adapters like the optical sata cables etc"" One thing I had tried from the service tech PDF was to try powering it on with out the processor installed. And as I mentioned the EFI DONE and GPU OKAY lights didn't stay lit during the boot process as they're supposed to and after removing the processor and installing 1 stick of ram, and holding the DIAG button all the proper status LEDS stayed lit up. I do not have a LGA 1366 motherboard to test the W3520 unfortently, but I am considering the possibility that I may have a failed processor? Even though when installed the CPU ERROR LED doesn't light up. Any and all help/advice is greatly appreciated.