My PC has a Q6600 processor overclocked to 2.8 GHz (312.5 FSB, or 1250 as it shows up in the BIOS) on a eVGA 680i TR motherboard. Although the 680i was quite excellent for overclocking the e6600, it isn’t so nice with the Q6600. I have the Q6600 paired up with the Zalman 9500 cooler from my e6600 days.
For quite some time, I tried overclocking my Q6600 beyond 2.8 GHz, without any success. I tried voltages on the RAM, other motherboard features, RAM timings, etc. Today, I installed Coretemp 0.99 and realized that my cooler was the bottleneck all along. If I run Prime 95, the core temperatures on all four cores (with a few degrees difference) reach the high 60’s! No wonder I couldn’t overclock beyond 2.8 GHz. And this is with the Q6600 on 1.2 volts in BIOS (CPU-Z says 1.184 volts). It idles at 45, 40, 40, and 44 degrees for each core respectively.
The moral of the story: make sure you keep a close eye on the CPU temperature when overclocking!