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Power consumption when overclocking

W

wildkatz84

Limp Gawd
Joined
Aug 19, 2008
Messages
166
I have a question...

If I take my CPU from 2.4GHz to say 2.8GHz... but leave the the core voltage the same does my cpu draw more power at the 2.8 speed then the 2.4 even though the Vcore is the same number?
 
The answe is Yes, (disregarding speed step and other utils that automatically reduce clock/mulitplier a low loads).

The new question is by how much and is it (until some extream frequency) a linear increase or not. The board will also use more power if for nothing else than the clock chip. There is no free ride.

--------------- I no longer think this is valid ----------------------------------------------------------------
And I think it is a fairly linear increase, whatever power it is using at 2.4 with the same load at 2.8 I think you can roughly calculate it as

original wattage x newspeed / old speed = new wattage

lets say Intel rates your cpu at 75W at 2.4 GHz (loaded) at 2.8, if I am correct, your new power dissipation would be.

75 x (2.8/2.4) = 87.5 watts

or you could think of it as a percentage increase.

2.8/2.4 = 1.166666 = a 16% increase in power used

The above is based on looking at Intel documents that show a mostly linear load line of voltage vs current. I could be all wet and if anyone has something different please post.

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Having trouble finding hard data on this, so it would be really cool if someone with a Kill-O-watt power meter would set their FSB at say 200MHz and raise it in 10MHz steps increasing the cpu working frequency and measue the power draw at idle in windows and at load with some stress software. While power supply effeciency etc. would affect the numbers a little, it should give some idea of what is going on concerning CPU frequency vs Power used. I cannot recall anyone doing such a thing over a wide range of cpu frequency and google has failed me.
 
Just by the 1st Law of Thermodynamics wouldn't there have to be a increase in power consumption given that you are running at a faster speed?
 
you have to remember Voltage isn't the only thing that goes into calculating power draw, while you won't draw any more Volt's you will draw more amperage, increasing your total watt usage.

Watt=Volt*Amp

as for specific formulas to determine the increase, I have none.
 
3 major influences on power consumption are clockspeed, CPU load and voltage.
Voltage is constant so clockspeed and load should be considered.

The CPUs internal resistance varies with speed and what it is doing.
This will vary the current drawn as mentioned earlier in the thread.
The faster the speed and/or higher the load, the lower the resistance and the higher the current flow.
Assuming the CPU is running at full load, a 10% increase in clockspeed will result in approx 10% increase power consumption.

Unless you run at full load a lot, the increase in CPU power consumption wont be that much from just overclocking.
 
The formula for power consumption of an ideal CMOS semiconductor is P = C*V^2*f, where C is a constant capacitance value, V is the voltage, and f is the switching frequency. In reality, there is wasted power, so the real power consumption is that formula plus waste. So technically the power usage should increase linearly with an increase in frequency; however, since real devices are non-ideal, there is really a greater than linear increase. The specifics of how much the difference is depends on the CPU itself, so there is really no way to know based on a generalized equation. You would have to test each CPU individually with proper power-measuring equipment, and even then there would be some error because there would be an increase in power consumption and in waste consumption of other items, like the chipset and the power regulation circuitry feeding the CPU.
 
OP, the short answer is yes, it does. As Zero82z pointed out, power increases somewhat linearly with frequency (so by going from 2.4GHz to 2.8GHz you'd increase the CPU's power consumption by at LEAST 16.6%, but likely a reasonable amount more). Also, power increases with the square of the voltage. So for example, if you went from 1.2 to 1.4v, even though the increase in voltage is the same percentage as the previous clock frequency increase (16.6%), power consumption would have gone up by a little over 36%.
 
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