Quote:
Originally posted by unregistered
interesting ideas there Since87
well, the second leg is the CPU's heat flux
any more clever thoughts ?
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How's this?
Watercool a system with chilled water so that the CPU diode indicates the same temperature as the motherboard in the CPU area. Now you know that no heat is moving through the pins. (There will be a temperature gradient across the motherboard under the CPU due to voltage regulators and other heat sources. The gradient will change too depending on how much current is flowing through the regulators etc., but you get the general idea. Epoxy copper sheet to the back of the motherboard to spread the heat around the CPU? Heatsink the MOSFETS of the voltage regulators?)
Insulate as for a TEC cooled CPU, so that air convection can't carry any heat away. 'All' the heat is going through the waterblock.
Since you know the C/W of the waterblock under the operating conditions, (+/- the error due to the CPU to Block TIM joint) you know the Heat output of the CPU.
As usual TIM joint error is the major problem. Regardless of how consistent you are when mounting to your die simulator, the curvature of the CPU die means that you won't get the same C/W through the TIM. I don't have a solution to that problem.
Ugly test with high probability of trashing a motherboard for questionable results.
Much more cleverness required.
BTW, WRT to the temperature diode stuff I mentioned earlier:
It occurred to me that the voltage output of the setup will be around 0.65 Volts with a +/- 0.01V swing over the entire range of temperatures you're likely to care about. It would be highly desireable to have a stable 0.65V source to 'null' against the diode voltage. This would allow the voltmeter to operate on the 0.1V range. (or even the 0.01V range if the voltage source was tweaked to match the CPU.) The diode voltage changes about 200uV/C, so this would help a lot with resolution. However considering the noise environment of a diode on a CPU, I'm not sure how much resolution can actually be useful.
Anyway, if you decide you want to do something with a CPU diode, let me know. I'll set something up for you.