Introduction

There are plenty of issues with current methods of comparing temperature data between processors, and we have been hard at work trying to come up with something that gives us better and more comparable results than the temperature data reported by different processors' thermal diodes. In considering different approaches, we have run into the same problem over and over: how do we measure the total heat output of the processor in any nearly accurate way.

The problem with thermal diodes is that between different architectures, there isn't really a way to compare what is being reported. The diodes only measure the temperature at a specific location, and the number we can pull out of a processor isn't necessarily representative of the average temperature of its surface.

Measuring the temperature increase of the system itself has issues as well. Different components in a computer heat up as well, and there's no way to really isolate the contribution of the processor itself to this process. The only number that can truly be compared between processors is the total energy output by the surface of the chip (or heat spreader).

The heat transfer from the CPU to the outside world would be a wonderful number to have, but there is the unfortunate necessity of a heatsink and fan for modern processors to run without cooking themselves. There isn't really a way for us to get to the surface of a chip in order to measure anything. So how are we supposed to measure how hot something is getting when we are required to be cooling it at the same time?

Well, there isn't any easy way we can think of, but just because something is impossible doesn't mean the AnandTech staff can't get it done.
Heatsink Modding: The New Rage
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  • Etacovda - Saturday, April 17, 2004 - link

    Yeah, id have to agree that the test was next to useless. The methods used were... archaic? to say the least. Put it this way, the AXP thats moved 1 deg under load generally should move in the region of 10 at least. so 1/10, applied to the prescott, would be a lot more... i know this method in itself is flawed ;) but thats the ghist of whats going on here.

    I hope you understand my point ;p
    Reply
  • Pumpkinierre - Saturday, April 17, 2004 - link

    #35 the heat capacity of air is small. If no heat sink were applied, MORE heat would be lost to the underside/mobo than the topside/heatspreader because the pins/traces/mobo act as a heatsink. Sure, if you place a liquid Helium 'cold finger' on the cpu you will get less heat loss from the underside but remember those metallic pins are linked to the heart of the die so thermal loss is inevitable. Slot 1/A would be better to cool (either side) but there would still be pin connection loss. If you replaced the die in the cpu packaging by a die size heating element with known power characteristics you might be able to produce a calibration curve in conjunction with fluid cooling or a temp. probe that would then be used to determine cpu power consumption. Of course, with the heating element measurements, the mobo is switched off with the cpu package/heating element sitting in the mobo sckt. I suspect Intel/AMD use a power flow determination as direct measurement is difficult.
    Reply
  • rwong48 - Saturday, April 17, 2004 - link

    like someone else said, i was wondering on the accuracy of these temperatures because the xp 2500+ barton only increased 1ºC from idle to load.. Reply
  • Coruscant - Friday, April 16, 2004 - link

    If you provide a cold enough heat sink (not the typical heatsink, but a source that absorbs heat) then the heat transfer to that heat sink will override the transfer from the processor sides/bottom to the ambient air. Additionally, so long as the ambient conditions are maintained, it would be reasonable to assume that the heat loss to through those surfaces would be comparable. Of course, assuming the surface temperature of all the processors in question are maintained at a pre-defined setpoint, the heat transfer from the processors to ambient would largely be the same, varying only by the difference in exposed surface area. Again, this would all be in the pursuit of determining at what rate of heat is generated be the various processors. Reply
  • MoronBasher - Friday, April 16, 2004 - link

    *unless i am wrong and they did enable cnq

    but the review wasn't that good altogether.
    Reply
  • MoronBasher - Friday, April 16, 2004 - link

    the article was missing something. they should have used the diode along with the probe. also, they should have used cool n' quiet for the athlon64 as that would be what is actually going on in real world terms.

    just my 2 cents
    Reply
  • mechBgon - Friday, April 16, 2004 - link

    The "percent increase" graph should be using Kelvins as a basis, not Celcius.

    For example, let's say a processor idles at 40°C and rises to 60°C under load. That's an increase of 20 Kelvins, or 20°C if you prefer, but it isn't a 50% increase... 40°C is 313 Kelvins, so a 20° rise is 20/313 or 6.4%.
    Reply
  • AIWGuru - Friday, April 16, 2004 - link

    The methodology used in this "test" wouldn't pass muster in a grade 4 science class.
    I can't believe that ANYONE is THIS inept.
    This article leaves me thinking that someone at Intel paid someone to write it.
    Reply
  • ZobarStyl - Friday, April 16, 2004 - link

    p.s. Not that I own one of those hunks of junk, but let's be honest that's where intel gets its cash, not from the enthusiast market. Reply
  • ZobarStyl - Friday, April 16, 2004 - link

    I would like to see a closed-case standard (same case and components, diff proc/mobo) with the internal case ambient being measured in different places. If Prescott is such a current hog, then (as was mentioned in relationship to electrical resistance above) other components such as the PSU might start adding heat to the total system. I don't run all these 80mm's to keep just the processor cool; I run them to keep all my components cool and keep system life at an optimum. If Prescott under load is 50 degrees but the sum of its output makes my case 15 Celsius hotter, then no amount of CPU speed will make me want to buy that. A processor is just one part of the system, albeit the most important, but that doesn't mean I want to buy every other component in my system twice because of premature thermal breakdown.

    Every computer case is a thermodynamic system straight out of a Physics textbook. Just because one component makes 10 degrees more heat doesn't necessarily mean the whole system can dissipate all that heat, and BTX aside Intel is going to have some serious issues running these things in major manufacturer style cases. I mean when the best cooling setup you get with a Dell is a single 80mm, and their smaller ones have no case fans at all, the Prescott is going spell early death for a lot of these systems.
    Reply

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