Heat from CPU (W) - Overclock.net

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post #1 of 18 Old 10-24-2006, 08:14 PM - Thread Starter
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I wrote a simple C++ program to find out how many watts of power an overclocked cpu produces.

It is based on this formula
Quote:
OC Wattage = TDP * ( OC MHz / Stock MHz) * ( OC Vcore / Stock Vcore )^2

The text "^2" means "squared".

This formula is fairly self-evident. The stock/OC MHz is just how fast the processor is meant to run, and how fast you are in fact running it. Same with the vcore, which to any new people is the voltage that is run through the processor. Higher voltage means more stability, but also can lead to much higher power consumption, and if excessive, and early demise.

The only term that needs explanation is the TDP, or Thermal Design Power. The TDP is meant to be the wattage of the processor at load. I say "wattage" because it is unclear if this is meant to corrospond most immediately to how much power is consumed in watts, or how much heat is produced in watts, but as near as I can tell the TDP is pretty much meant to indicate both.

To get your processor's TDP, you must depend on AMD or Intel's own figures. In the case of AMD's XP line both maximum and typical are listed, and typical is what you want. Maximum is apparently if every single transistor were powered at the same time, which will never happen. Typical is meant to be the realistic maximum wattage.
source

here is the program and source code if anyone wants to see it. Its an easy program, but my math is kind of wierd at some points in the program so feel free to make suggestions. Attachment 33782

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post #2 of 18 Old 10-24-2006, 08:26 PM
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sweet

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post #3 of 18 Old 11-03-2006, 07:10 PM
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...Java...

Mine comes out to 102.44W- Does that sound right?

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post #4 of 18 Old 11-03-2006, 07:15 PM
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Hey Buddy, Thanks I just down loaded and tried it...Very Nice.......

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post #5 of 18 Old 11-03-2006, 07:46 PM - Thread Starter
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Quote:
Originally Posted by Burn View Post
...Java...

Mine comes out to 102.44W- Does that sound right?
depends it should be right but you could do it out by hand to make sure it works
I know I checked the prgram using sdumpers numbers for his conroe and it worked so.

Edit: whats your overclock and vcore?

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post #6 of 18 Old 11-03-2006, 07:49 PM
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I did it through my calculator- The equation seems right, I cross-checked it on another site's CPU wattage calculator, same spec.

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Originally Posted by CyberDruid
Burn + Electricty + Water =
But the man has the patience of a saint...
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post #7 of 18 Old 11-03-2006, 07:49 PM - Thread Starter
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Quote:
Originally Posted by Burn View Post
I did it through my calculator- The equation seems right, I cross-checked it on another site's CPU wattage calculator, same spec.
ok good some of the math is a bit messed up as I said. It comes out with the right answer just some of the steps to get to it are odd.

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post #8 of 18 Old 11-03-2006, 07:54 PM
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I screwed the math up the first time- I accidentally switched around speeds (stock speed/overclocked).

My CNC Mill Project
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Originally Posted by CyberDruid
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post #9 of 18 Old 01-13-2007, 11:20 PM
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Nice program however it is not very accurate. The problem is, the voltage you set in BIOS never reaches your CPU. This is caused by Vdroop. Also, your formula will not produce an accurate value because:

A. The TPD is not the amount of heat that a C2D puts out, however, it is the amount of heat the cooler is expected to dispell. The C2D may really put out 40 watts or even less.
B. The processors Mhz has no correlation to heat output, as far as I am aware.

Now if you could measure the Amps and voltage going to the CPU, you could calculate CPU wattage.

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post #10 of 18 Old 01-13-2007, 11:46 PM - Thread Starter
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Quote:
Originally Posted by pauldovi View Post
Nice program however it is not very accurate. The problem is, the voltage you set in BIOS never reaches your CPU. This is caused by Vdroop. Also, your formula will not produce an accurate value because:

A. The TPD is not the amount of heat that a C2D puts out, however, it is the amount of heat the cooler is expected to dispell. The C2D may really put out 40 watts or even less.
B. The processors Mhz has no correlation to heat output, as far as I am aware.

Now if you could measure the Amps and voltage going to the CPU, you could calculate CPU wattage.
The program may not be extremely accurate, but it isn't bad for approximations.

A. TDP represents the maximum amount of heat the cooling solution is expected to dissipate(as you said). The figure is high by default from the manufacture because the processor will never reach that heat level? So I guess the program doesn't calculate the total amount of heat, but maybe just how much the heatsink will have to dissipate in order to keep the chip in an acceptable temp range.

B. Raising the clock speed of a chip will increase its thermal output even if there is no increase in the voltage. I have seen an explanation for it but at the moment I can't find one .

Thanks for the input

~jrs

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