Hi, I upgraded my 2009 Mac Pro with 2 X5660s and so far I am loving it. I know that the X56xx westmere series are supposed to run cooler than the older X55xx processors and from what I can tell from iStats it does !! Only thing is, I was also hoping my northbridge temps would be lower as well and it is not the case, the temp is the same 79C idle which I heard is fine, but still sounds high to me. I up-ed the exhaust and intake fan to cool down the temp of the northbridge to 69C but then the processor speed (BOOSTA, BOOSTB) are up 1450 rpm and more audible .. bummer. trying to see if there could be a potential hardware mishap somewhere I decided to run the AHT tools at boot and it just froze at the scanning hardware step. I figured the AHT I have is for the 2009 Mac pro and maybe it is not compatible with the firmware-hacked 5,1 machine I have now. Does anybody know if we are supposed to use the Mac pro 2010 AHT software for a 2009 5,1 machine ? ---------- oops ! I posted too fast .. never-mind my silly question, a quick search in the forum showed that indeed you have to use the AHT for the mac pro 2010 if you flashed the firmware of your 2009 machine.