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I was hoping I wouldnt have to ask this did a few searches on the net and still cant get a good explenation...
What does C/W mean?
What does C/W mean?
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www.overclockers.com said:To calculate what to expect for other CPUs, for every watt the CPU radiates, the heatsink will cool the core by the (C/W x watts) plus ambient temp. For example, at a fan inlet temp of 25 C, a C/W of 0.25 with a CPU radiating 50 watts means that the CPU temp will be 50 x 0.25 = 12.5 C over ambient temp, or 37.5 C.
Yes, the example from overclockers is correct. That’s why I referred to it.johan851 said:Graystar - I copy/pasted from www.overclockers.com. Their example is correct, no?
Yes, C/W is a division as per the formula:Yamiyanazz said:That's what I figured it to be. Possibly the "c/w" stands for "celcius *over* watt"? If you take the difference in celcius and devide it by the wattage it's cooling, you get the c/w rating. That's what I've concluded anyway.
Graystar said:In our context, C/W refers to a measure called Thermal Resistance. It is the standard unit of measure used by the heatsink industry to measure heatsink performance. Thermal resistance is the measure of a substance’s resistance to heat flowing through it. For example, the “R” value rating that you see on home insulation is actually a thermal resistance value. The higher the R value is, the greater the resistance to heat flow, and hence the better the insulation.
When referring to heatsinks and waterblocks, you want as little thermal resistance as possible. Heatsinks with low thermal resistance allow heat to flow through faster. And since the job of a heatsink is to move heat, lower is better.
Thermal resistance is calculated by dividing temperature change by heat dissipation. The temperature is measured in degrees Celsius. Heat dissipation is measured in watts. So C/W is Degrees Celsius per Watt.
So lets look at that previous statement posted by johan851:
"First, understand what C/Ws are telling you: The difference between a heatsink with a C/W of 0.30 and 0.35 is 5 C at 100 watts under stress. At 50 watts, it's half that."
A C/W of 0.30 actually means a change in temperature of 0.30 degrees Celsius for every watt of heat that is to be dissipated. If you have 100 watts to dissipate, then you’ll have a 30 degree change in temperature within the first heatsink.
As before, a C/W of 0.35 means a change of 0.35 degrees for every watt of heat that is to be dissipated. If you have 100 watts to dissipate, then you’ll have a 35 degree change in temperature within the second heatsink.
The second heatsink is hotter. It’s hotter because it isn’t allowing heat to pass through as easily as the first heatsink does. Why is this bad? Because a hotter heatsink won’t transfer as much heat from the CPU as a cooler heatsink will.
Temperature = Thermal Resistance * Heat Dissipation
Thermal Resistance = Temperature / Heat Dissipation
Heat Dissipation = Temperature / Thermal Resistance
No. But that was a nice try, though.johan851 said:And that temp change is relative to ambient. So to figure out the temperature a heatsink should give you, take the C/W, multiply by processor output wattage, and add ambient. So...
.19 x 70 + ambient = temp.
Right?
I hate to be the one to break it to you, but Newton’s laws don’t dictate anything because they’re all in the realm of classical physics. Quantum physics is the way things really are (well, at least until something else comes along.) Sorry.Restorer said:I've always found these ratings confusing, if not worthless...
Graystar said:I hate to be the one to break it to you, but Newton’s laws don’t dictate anything because they’re all in the realm of classical physics. Quantum physics is the way things really are (well, at least until something else comes along.) Sorry.
Yeah, that's what they keep saying...but they just can't get it to work! Personally, I think string theory is hangin' by a thread.Tovas said:String Theory