Well, I've done a few of these already, and this is the first time I have a problem; I'm hoping someone here can help me out.... The system is a 2010 Mac Pro (2x2.4GHz version). I wanted to upgrade the chips to two X5670 hexcores. I only have one chip for now, so here is what I did: I pulled out both original chips, and put the hexcore in the CPU A socket. I placed a CPU blank over socket B, and then placed the heatsink over it (gently, just enough to connect to the fan connector on the processor tray. I attached the heatsink over CPU A as normal. I have filled up the four memory slots for CPU A, so as to have 16GB. Then I turn it on. Everything works fine, except for two things: 1) About 15-30 seconds after arriving at my desktop, both "lower" case fans start running full blast -- very loud! 2) My 16GB RAM are recognized, but only at 1066 speed (should be 1333). I tried resets on the SMC and PRAM, but nothing changes. I pulled out the processor tray to check heatsink connections, and all looked great. Anyone know what the trouble might be? Rightnow, I'm stumped.