|Intel Core-i3/i5/i7 LGA1156 Overclocking Guide|
|Articles - Featured Guides|
|Written by Servando Silva|
|Tuesday, 24 August 2010|
Page 8 of 10
Overclock vs Power ConsumptionSome people cry a lot about power consumption (including me). I'm the kind of person who wants the best efficiency if possible, and that means I want my CPU as fast as I can without doubling power consumption. As if we didn't had enough with all the extra components already! Reality is, many people don't even bother about power consumption, and after all, that's why they paid for 800 watts PSU (even if they normally don't use more than 300 watts). Anyway, I'll test both Idle and Prime 95 modes and measure overall PC power consumption with a p3 international kill-a-watt meter. Have a look at the next results as they represent power consumption (without monitor or external peripherals) in idle mode. This numbers are important as you probably keep your PC near idle mode 70% (or more) of your time.
As you can see, power consumption increases a little when you overclock with stock voltage. Maximum difference was 6 watts represented by the Core i7 860, while the Core i3 and Core i5 processors only increased 2-4 watts in idle mode. A 3% increment in idle mode compared to the 25-30% increase in MHz makes this look as the highest efficiency setup of all them. Anyway, we can only make conclusions after analyzing Full Load results, but I hope they won't increase that much. Increasing CPU vCore to 1.3v still adds a little percentage to the power consumption; however, the slope inclines a lot more when going to 1.5 volts as you can see in the chart. Now, let's have a look at Full Load (Prime95 Blend Test) results:
Ok, now we're talking... The Core i7 860 quickly reached 180 watts at full load, against 125-133 watts at load for the rest of the CPUs. Overclocking with stock voltage increased 3-4 watts on Clarkdale's processors while it increased 10 watts for the Lynnfield's CPU. In this case, the slope becomes bigger at 1.3v, especially the Core i7 860 which already passed 205 watts. The Core i3 is still doing fine with 10 extra watts over stock frequencies, and the Core i5 655K is consuming 15 extra watts compared to stock frequencies. I think it would be wise to say 1.3v is the maximum vCore accepted to keep efficient results at the end. Notice how the slope inclines a lot more with 1.4v and 1.5v? Those results make overall efficiency go down and you shouldn't apply it unless you don't care about power consumption or you're aiming for benchmark results only.
Of course, increasing power consumption means the CPU heatsink will have more watts to dissipate, thus increasing CPU temperatures. Let's have a look at our voltage vs. temperature results in the next page then.