MP 1,1-5,1 Mac Pro 5,1 doesn't boot after cpu upgrade

[arifercos]

A couple of months ago I replaced my dual E5520's with X5680's. My mac pro ran fine for a couple of months and one day, it randomly froze. I had to force restart it and it never booted up again. The fans spin up, but no chime and nothing on the screen. I installed my old CPU's back in and everything works fine.

I thought the problem was with the psu, so I replaced it. The mac booted up again, but after 5 minutes it froze up again. The same problem occured: fans spin up, no chime/boot. What could the problem be?

My current config:
- Mac pro 4,1 flashed to 5,1
- Dual X5680's
- 48GB RAM
- R9 280X

 

[reader50]

What do the diagnostic LEDs say on the backplane and processor boards?

Do you have another GPU available? If so, try swapping them for awhile. The 280X is quite old today. If it's failing (or HS grease dried out) that could explain all symptoms.