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I have purchased a new HP PC (EliteDesk 800 Small Form Factor).

It is exceptionally quiet, I assume HP favors quietness over thermal performance for office use.

Under load (long-running calculations, all 4 cores 100%) the CPU temperature never exceeds 62C (144F), which is good.

However, the ambient temperature inside the rear of the case rises to about 42C (108F). This is clearly due to the heat being dissipated by the CPU cooler. I took the measurement using an accurate probe-type thermometer by sticking it in the rear of the case:

enter image description here

I'm concerned. Is 42C (108F) getting too hot in there?

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  • In comparison, my own custom-built PC (similar specs to the HP) never goes above 35C (95F) ambient. But it is a much louder.
    – misha256
    Jan 22, 2015 at 6:36

2 Answers 2

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What you’re measuring is the exhaust temperature of the CPU cooling unit. As you can see on the following image, this air outlet is directly connected to the cooling unit. There’s no way the air is that hot before passing through the CPU cooler.

stolen image #435

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  • You're absolutely right, can't believe I didn't see this myself. I should have just opened the case and had a look. So HP have created a tunnel, and the CPU fan effectively doubles as an exhaust fan. I think I like the design, it's so quiet!
    – misha256
    Jan 22, 2015 at 10:00
  • @misha256 It’s a relatively popular design with small(-ish) form factor PCs. It allows for more efficient cooling, after all.
    – Daniel B
    Jan 22, 2015 at 10:12
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Yes, it is. No parts will burn, melt or flex (become less rigid) as such temperature. It is a tad high, as usually you want it close to room temperature, but for a general office PC with only minimal of fans installed, 42c is fine. I suggest speedfan ( http://www.almico.com/sfdownload.php ) to check AUX (ambient value) temperature. This should also reveal any other temperature sensors inside. Beware that the AUX sensor may show bogus results, expected is that it is between room temperature and CPu\GPU temperature, if it's a lot higher or lower, it's bogus. Known possible bug in speed fan.

Alternate software is HWmonitor, I use this together with speed fan to compare measurements and lie down an average. It also struggles less with showing ambient temperature. You can get it here: http://www.cpuid.com/softwares/hwmonitor.html

If you want to lower ambient temperature in a simple way, see if you can install some 140 mm fans. Best is one to blow out from the back, and one to suck in on the front or side. If you can't fit 140mm, simply use the larges that seems to fit. Usually those computers come with only 1 fan in the back to suck out + the CPU fan.

The important part is to keep your CPU and GPU (graphical processing unit) under ~75-80c, as a higher value may indicate that the cooling paste is in need of a change, or something else is hindering proper cooling, such as dusty cooling ribs over the CPU.

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  • Up-voted for your recommendation to use temp monitoring software to get a better picture of what's going on.
    – misha256
    Jan 22, 2015 at 10:02

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