It just turns on and sits there with the fans running slow. What is also strange is it never gives a blinking power light or lights on the board itself. Tried at least half a dozen times thinking it wasn't seating right, swapping out washers, memory, drives, video cards etc. However could not get it to work with the CPU B. Booted up fine and got a Geekbench score of ~14K with just the single processor! Of course the fans were going full blast. I used 2 M4 1mm nylon washers and my CPU A install went fine. Unfortunately I wasn't so luckily with my dual x5660 upgrade. I do have non ECC ram, but I wouldn't think it'd show the above symptoms if RAM is incompatible? The RAM works fine with the current Nehalem Xeon's E5520 This is where I am at now, unsure why I cannot get it to post with a single X5660. This works fine, the Mac pro posts, and I hear the chime followed by the gray Apple boot screen. I then tried putting the original Nehalem Xeon E5520 2.26GHz back. I then tried again but this time with the 2nd Xeon X5660 in CPU socket A, same result.īy now was getting worried I fried something, so I check the LGA socket couldn't find any bent pins.

Checked 2mm extra thermal pad on voltage regulators. Tried a few things here, removed and reseated CPU, reapplied Arctic S5 etc, made sure the heatsink thermal/fan connector is plugged in all the way. Then the OVTMP CPU A Led lit up on the logic board. I now got a solid power light, but a few secs later I got a RED LED next to the thermal/fan connector on the processor tray CPU A. I tightened the heatsink some more according to the guide. I first tried just CPU A, installed the board and tried booting the Mac Pro, initially I got no POST and a blinking power light. I read up on several threads, and largely the followed this guide I tried to install them tonight and failed so far. Ok I ended up getting 2 of these Xeon X5660

Upgrade 8 core mac pro to 12 core