Question about OC and power

[eli2k]

Quick question about overclocking and its effect on power consumption. If I have a 2.0ghz with TDP 65W and I OC to 3.0ghz, and I have a second processor that is 3.0ghz with TDP 65W, does the OC TDP increase by a large amount? Lots of people say, get this cheaper CPU, because you can OC it so easily and it is fine with the stock air cooler, but I'm assuming if Intel binned the particular chip, then OC by increasing voltages and upping FSB should technically increase power, right?

Thanks,
- Eli

[Lsdmeasap]

Re: Question about OC and power

Right

[randomness]

Re: Question about OC and power

of course the OC will increase the TDP, remember tDP is only valid when running at stock speeds AND at 100% cpu load.

y is 3GHZ still at 65W? its probably cause of the multiplier, a 3GHZ cpu will have a higher multiplier, but its FSB will be fixed at xxxMhz.

BUT a 2ghz cpu running at an fsb of 333 [assuming it is OC] obviously would hav a higher TDP than 65W.

In a nutshell, of course OC will increase power consumption.

[johnerz]

Re: Question about OC and power

And anyone who overclocks on the stock cooler should sit in a dark corner and think hard about it :)

[Chucko]

Re: Question about OC and power

As a general guideline, power consumption goes up linearly with clock frequency, but increases as the square of the voltage.

Here's a hypothetical example. Say your 1GHz processor runs at 10W TDP. You overclock it to 1.5GHz at the stock voltage; now it uses 15W. You try to really push it, so you get a 100% overclock to 2GHz, but you have to raise the voltage by 40% to get there. Raising the voltage 40% doubles the power consumed, plus it's now running twice as fast, so you've doubled the power requirement again, and your chip now burns 40W!

In practice I think it's even worse than this - power usage goes up more than linearly with frequency as you get close to the chip's limit.

This is why it's good to keep voltages as low as possible. Dropping the voltage 10% reduces power usage by 19%; dropping voltage 20% will reduce power usage by 36%.