Hi, I have a mac pro 4,1 dual 2.26Ghz gainestown processors. The machine started to become unstable and after doing a hardware test, I got a failure from the Northbridge sensor hitting 123 degree C which is why the mac was so unstable I ssumed. One day it didn't post and after opening it I realizes some of the black plastic pins that holds the northbridge heatsink in place were broken. I took the mac to the apple store and they had me replace the whole processor board for $300. Now my mac is ok, and after running the hardware tests (slow and fast), everything passes. But, I am still concerned as iStats and other temp software show the northbridge chip temp at 79c at idle .. when I cold boot, the temp starts in the 50c but then after 5 min plateau to 79c. Doing some stress tests or using the computer for a while the temp usually stays at 79c sometimes 80c .. Should I be worried ? PS: I have read other posts on this forum about lower temps (65c) for the northbridge chip but they were for single proc mac 5,1 with westmere proc (running cooler than gainestown). Anybody care to share their northbridge temps for dual proc nehalem on mac pro 4,1 ? Thanks !