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I just upgraded my Mac Pro 4,1 (5,1 firmware) to dual X5690s. I was very careful and followed directions throughout the whole process.

When I put the CPU tray back in, the computer wouldn't post. There are no hardware errors, but it won't boot. I have tried an SMC and NVRAM reset to no avail. Upon pressing the power button, the power light turns on and remains lit. No red LED problem lights appear in the computer. The GPU fan speeds up to full, like it always does on a boot, but then instead of slowing down, it remains at full. All other fans are at normal speeds. My boot drive is an SSD on a PCIe SATA adapter.

Everything was working normally this morning before my project. Any troubleshooting suggestions?

(I've heard maybe tightening the heat sinks down more, but I don't want to over tighten them.) Also, the first time I tested the upgraded tray, the power button was flashing, so I tightened the heatsinks a bit more.

Any help would be appreciated!

  • Try unplugging, and removing the battery, for a few minutes. It might be the case that some fault or other status is held in CMOS that is inhibiting your startup. – Whit3rd Dec 24 '16 at 1:31
  • I replaced the original CPUs and it boots ok. I'm replacing de-lidded CPUs with lidded ones but the CPUs should work. I know X5690s are compatible with my computer. Is it possible to test a processor without putting it into my Mac Pro? I'd like to know if I received broken processors – NoahL Dec 24 '16 at 1:35
  • Also, I now have two unresponsive DIMMs. Could it be related to the work I was doing replacing the processors. (Note it's the DIMMs not the RAM sticks that are not responsive). – NoahL Dec 24 '16 at 1:45
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Processors either work or they don't. As long as they are siting in their sockets correctly. Tightening the heatsinks is unlikely to do anything, but be careful not to over tighten as you could damage something if you do.

You could take them out and verify the sockets are clean and free of obstructions and that there are no bent pins. You could also swap which socket which proc is in. I know that doesn't make sense but sometimes it just works that way.

Try with the old Procs in place if that is possible. If they work then you may have the wrong upgrade processor(s) or a defective one or two.

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