Why do you care? Heat (power) increases with the square of voltage. It increases in a linear fashion with frequency. What does that mean? It means that as your FSB goes up, so does your heat, but as your vcore goes up, your heat goes up exponentially.
An increase in processor operating frequency not only increases system performance, but also increases the processor power dissipation. The relationship between frequency and power is generalized in the following equation: P = CFV^2 (where P = power, C = capacitance, V = voltage, F = frequency). From this equation, it is evident that power increases linearly with frequency and with the square of voltage.
I quoted the above statement from an Intel document. It has been removed from intel.com and used to reside at the following link:
Missing Intel Document. I managed to find a copy of the pdf file in one of my backup sets. Knuspar from guru3d kindly agreed to host it
here.
The title of the document is, "Intel® Core?2 Extreme Quad-Core Processor QX6700? and Intel® Core?2 Quad Processor Q6000 ? Sequence Thermal and Mechanical Design Guidelines." It?s dated Jan 2007 and has an official Intel Document Number of 315594-002. I managed to find a copy of the pdf file in one of my backup sets -
here is a screenshot of section 4.1 on page 31 which is where the above quote came from.
To illustrate, consider this analysis of two difference vcore settings and the temps they produce on my Q6600 @ stock settings (9x266=2.40 GHz) as well as running overclocked (9x333=3.00 GHz). The two voltages I used were 1.1375V and 1.2625V set in the BIOS that correspond to the two clock levels of 2.40 GHz and 3.00 GHz respectively. In case you?re wondering, these translated into 1.112V and 1.232V in Windows as read by CPUZ.
Prime95 ran for 30 minutes and the temperatures were averaged over the last 10 minutes of those runs (well after they stabilized). Room temp was 75-76 °F. Notice that the difference in voltage is ONLY 0.120 V or 120 mV, but this seemingly small difference brought the load temps up by an average of 6-7 °C per core!
Run1 (9x266 @ 1.112 V), Average temps (°C): 51,52,50,50
Run2 (9x266 @ 1.232 V), Average temps (°C): 57,58,57,57
Differences (°C): +6, +6, +7, +7
Now if I add a faster FSB, they increased further:
Run3 (9x333 @ 1.232 V), Average temps (°C): 61,61,60,60
Differences from lowest voltage (°C): +10, +9, +10, +10
Differences from same voltage (°C): +4, +3, +3, +3
The same thing holds true for speed in a car: energy = 0.5mv^2 where m is mass and v is velocity. This is the basis of the old expression, "speed kills." You generate way more energy driving 75 MPH than you do driving 55 MPH since energy and velocity have an exponential relationship. Take a 5,500 lb SUV as an example; its energy nearly doubles as a result of that mere 20 MPH increase.
Energy @ 55 MPH = 754 kJ
Energy @ 75 MPH = 1,402 kJ