I thankfully received that reassuring short beep, and the system booted up properly. I launched CPUZ, if for no other reason, to admire my new CPU speed. I launched CoreTemp to check out the temps, which were in the low 30s and nothing to worry about.
When I first undertook overclocking, back in the Socket A days, my main reason was to increase my CPU speed to that of the next model. Well, I have more than accomplished that here, as my 2.7gHz overclock has surpassed that of the Q6700, clocked at 2.66gHz, and costing over $100 more than the Q6600 when they were first released.
Now the decision is whether to stop here, or keep going. Since the procedure is the same, I'll stop here, but discuss what happens when going on to overclocking bliss.
You will eventually get to the point where your overclock causes the CPU to be too unstable to run properly. If you are increasing the FSB by small increments, Windows may start fine, but a benchmark or game may cause the system to crash. Sometimes the system will POST, but will crash during the launching of Windows. Other times, the system won't post, but this usually happens when increasing the FSB by larger increments.
When this happens, go back into the BIOS. If the system wouldn't POST, you won't have any choice. You have two options, either back off the overclock until stability is attained, or increase the Vcore or CPU voltage.
Increasing CPU Voltage:
Increasing the operating speed of your CPU also increases the heat produced by it. Raising the Vcore really increases the heat. I highly recommend that you don't increase your CPU if you are using a stock cooler. Besides the heat issue, applying too much voltage is the quickest way to make a paperweight out of your expensive CPU.
Some BIOS let you see the current CPU voltage, others don't. Some BIOS let you increase the voltage from the current one, others, such as this one, have a list of voltages from a very low voltage to a very high one, which is why I suggested jotting down your current Vcore before beginning. A little voltage goes a long way; the increases are usually in .01 or .0125 increments. I usually increase by .02v/.025v at a time.
So the procedure is increase CPU Voltage until your overclock is stable. If you are continuing the overclock process, it will be a see-saw between raising CPU speed and voltage, watching your CPU temp all the while. I don't feel comfortable with my CPU idle temp getting over the mid 60Cs.
Eventually, you will reach a point where you cannot get the system stable enough to POST regardless of what you do. Back off your CPU speed to a point where stability is attained at idle. Keep in mind that there are other factors that can hold back your overclock, especially the motherboard. On various motherboards, I've had this Q6600 maxed from 2.85gHz to 3.45gHz. There are various reasons for this, usually having to do either with Northbridge stability, or voltage stability coming from the motherboard's power supply. Other reasons include the ever-common cheap or too-small PSU.
At this point, most people run Prime95 to check for CPU stability. Prime95 finds prime numbers and checks the results against the correct answers. Instability in the CPU will eventually give wrong answers. Successfully running Prime95 for 8-12 hours certifies the rig “Prime95 stable”.
Be aware that Prime95 doesn't always find memory instability. If you are overclocking your memory along with the CPU, it is very possible to pass Prime95, but crash the system with a very memory intensive application, such as the games Crysis or Supreme Commander.
