# CPU cooling info FYI



## MMacD (Mar 20, 2017)

I have an AMD FX8320 chip in my workhorse machine and, being always interested in keeping my systems frosty, I bought it a Delta AFB0712VH-A fan of its very own to replace the rather cheesy fan that came with the aftermarket 70mm Rosewill heat sink.

The heat sink itself is impressive--a BIG chunk of aluminum--but that fan is wonderful.  52CFM, 0.433 static pressure in H2O, 5.28W, 47.5dB(A).  With the system idling, the on-chip sensor reports 7C(!) in ~24C ambient.  With the system (10.3 RELEASE) working hard to filter a huge file, the CPU goes all the way up to 27C.

So, if you need a CPU fan for a 70mm heat sink, consider the Delta AFB0712VH-A.


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## morbit (Mar 21, 2017)

If I've understood you correctly regarding your cooling setup, that's Nobel-worthy achievement.


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## Eric A. Borisch (Mar 21, 2017)

morbit said:


> If I've understood you correctly regarding your cooling setup, that's Nobel-worthy achievement.



I was going to suggest patenting it.

It sounds like the calibration (or the reading of it) is wrong on your CPU temperature. Assuming you've got just the fan -- no compressor or other active cooling technique -- better fans can only get you closer and closer to ambient.


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## MMacD (Mar 21, 2017)

I can only go by what sysctl and amdtemp (which I suppose might just be echoing sysctl) claim that the chip is reporting.  I try to keep the room at an indicated 50% humidity, so there's a certain amount of moisture that could perhaps serve as evaporative coolant (cf. swamp coolers), but apart from that I don't know what to tell you.  I'm not making it up.


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## aragats (Mar 21, 2017)

Here is an example of wrong temperature reported from time to time by my i7-3520M:
	
	



```
acpi_tz0: _CRT value is absurd, ignored (200.1C)
```


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## MMacD (Mar 21, 2017)

aragats said:


> Here is an example of wrong temperature reported from time to time by my i7-3520M:
> 
> 
> 
> ...


How often does yours get it wrong?  My one is at least consistent, fwtw.


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## aragats (Mar 21, 2017)

It looks to happen once an hour in average, I don't have timestamps in /var/log/dmesg.today to be more precise.
I have to check what sysctl(8) reports when it happens, currently everything is normal:
	
	



```
$ sysctl dev.cpu | grep temperature
dev.cpu.3.temperature: 38.0C
dev.cpu.2.temperature: 38.0C
dev.cpu.1.temperature: 46.0C
dev.cpu.0.temperature: 47.0C
```


```
$ sysctl hw.acpi.thermal.tz0.temperature
hw.acpi.thermal.tz0.temperature: 44.1C
```


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## MMacD (Mar 21, 2017)

It mightn't be meaningful, but mine was around 35-45C also --at idle!-- before I fitted the new fan.  And that was the reason I bought the fan--idling at ~100F despite a big chunk of heatsink and a fan seemed excessive.


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## Eric A. Borisch (Mar 21, 2017)

Hrmm, still not buying 7C chip in 27C ambient with just a fan. I wonder if this is still the case:

http://forums.guru3d.com/showthread.php?t=376926

You might watch the reported temperature while gradually adding load and see if there is a big jump. Life from, say, around 10 to 30 as shown in the graph.

Sensing temperature with solid state isn't as simple as you might think, and you generally design/calibrate around the region you actually care about -- hot in this case.


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## MMacD (Mar 21, 2017)

Eric A. Borisch said:


> Hrmm, still not buying 7C chip in 27C ambient with just a fan. I wonder if this is still the case:
> 
> http://forums.guru3d.com/showthread.php?t=376926
> 
> ...



Good idea -- I'll research that.


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## MMacD (Mar 22, 2017)

Okay, I installed stress-ng and, after tee-ing up a loop to watch the temp at half-second intervals, called the stressor with `stress-ng -c 8 -t 60 -v` (8 cp jobs for 60 seconds).  The temp trace _appears_ to show a fairly simple increase and decrease that maps onto the jobs that are claiming cp time, e.g. xorg, xfce, the shell itself, Firefox, etc.  There's an apparent 10C step when the stressor starts up (6.8C to 16.3C in 0.5 sec. I might try a 0.1 second interval to see whether the step is just a reflection of granularity), and the cooldown after the stressor's jobs run to completion seems to show a very reasonable falling slope.


```
dev.cpu.0.temperature: 6.6C
dev.cpu.0.temperature: 6.6C
dev.cpu.0.temperature: 6.6C
dev.cpu.0.temperature: 6.6C
dev.cpu.0.temperature: 6.6C
dev.cpu.0.temperature: 7.2C
dev.cpu.0.temperature: 7.5C
dev.cpu.0.temperature: 7.6C
dev.cpu.0.temperature: 7.2C
dev.cpu.0.temperature: 7.1C
dev.cpu.0.temperature: 7.1C
dev.cpu.0.temperature: 7.1C
dev.cpu.0.temperature: 6.8C
dev.cpu.0.temperature: 6.8C
dev.cpu.0.temperature: 6.8C
dev.cpu.0.temperature: 6.8C
dev.cpu.0.temperature: 16.3C
dev.cpu.0.temperature: 16.7C
dev.cpu.0.temperature: 17.6C
dev.cpu.0.temperature: 18.7C
dev.cpu.0.temperature: 19.2C
dev.cpu.0.temperature: 20.0C
dev.cpu.0.temperature: 20.1C
dev.cpu.0.temperature: 20.7C
dev.cpu.0.temperature: 20.8C
dev.cpu.0.temperature: 21.1C
dev.cpu.0.temperature: 21.3C
dev.cpu.0.temperature: 21.7C
dev.cpu.0.temperature: 22.2C
dev.cpu.0.temperature: 22.2C
dev.cpu.0.temperature: 22.5C
dev.cpu.0.temperature: 22.8C
dev.cpu.0.temperature: 23.1C
dev.cpu.0.temperature: 23.3C
dev.cpu.0.temperature: 23.5C
dev.cpu.0.temperature: 23.7C
dev.cpu.0.temperature: 24.1C
dev.cpu.0.temperature: 24.2C
dev.cpu.0.temperature: 24.7C
dev.cpu.0.temperature: 24.3C
dev.cpu.0.temperature: 25.0C
dev.cpu.0.temperature: 24.7C
dev.cpu.0.temperature: 24.7C
dev.cpu.0.temperature: 25.3C
dev.cpu.0.temperature: 25.1C
dev.cpu.0.temperature: 25.6C
dev.cpu.0.temperature: 25.3C
dev.cpu.0.temperature: 25.5C
dev.cpu.0.temperature: 25.6C
dev.cpu.0.temperature: 25.7C
dev.cpu.0.temperature: 25.7C
dev.cpu.0.temperature: 25.6C
dev.cpu.0.temperature: 25.5C
dev.cpu.0.temperature: 25.5C
dev.cpu.0.temperature: 25.8C
dev.cpu.0.temperature: 26.3C
dev.cpu.0.temperature: 26.3C
dev.cpu.0.temperature: 26.5C
dev.cpu.0.temperature: 26.5C
dev.cpu.0.temperature: 26.3C
dev.cpu.0.temperature: 26.7C
dev.cpu.0.temperature: 26.8C
dev.cpu.0.temperature: 27.0C
dev.cpu.0.temperature: 27.2C
dev.cpu.0.temperature: 27.2C
dev.cpu.0.temperature: 27.3C
dev.cpu.0.temperature: 27.3C
dev.cpu.0.temperature: 27.6C
dev.cpu.0.temperature: 27.7C
dev.cpu.0.temperature: 27.5C
dev.cpu.0.temperature: 27.7C
dev.cpu.0.temperature: 27.5C
dev.cpu.0.temperature: 27.5C
dev.cpu.0.temperature: 27.7C
dev.cpu.0.temperature: 27.7C
dev.cpu.0.temperature: 27.6C
dev.cpu.0.temperature: 27.8C
dev.cpu.0.temperature: 27.8C
dev.cpu.0.temperature: 27.7C
dev.cpu.0.temperature: 28.1C
dev.cpu.0.temperature: 28.2C
dev.cpu.0.temperature: 28.1C
dev.cpu.0.temperature: 28.5C
dev.cpu.0.temperature: 28.2C
dev.cpu.0.temperature: 28.3C
dev.cpu.0.temperature: 28.3C
dev.cpu.0.temperature: 28.5C
dev.cpu.0.temperature: 28.6C
dev.cpu.0.temperature: 29.2C
dev.cpu.0.temperature: 29.3C
dev.cpu.0.temperature: 29.2C
dev.cpu.0.temperature: 29.3C
dev.cpu.0.temperature: 28.8C
dev.cpu.0.temperature: 29.5C
dev.cpu.0.temperature: 29.6C
dev.cpu.0.temperature: 29.7C
dev.cpu.0.temperature: 29.7C
dev.cpu.0.temperature: 29.7C
dev.cpu.0.temperature: 29.6C
dev.cpu.0.temperature: 29.7C
dev.cpu.0.temperature: 29.8C
dev.cpu.0.temperature: 29.8C
dev.cpu.0.temperature: 30.1C
dev.cpu.0.temperature: 30.1C
dev.cpu.0.temperature: 29.8C
dev.cpu.0.temperature: 30.1C
dev.cpu.0.temperature: 29.6C
dev.cpu.0.temperature: 29.8C
dev.cpu.0.temperature: 30.1C
dev.cpu.0.temperature: 29.8C
dev.cpu.0.temperature: 30.2C
dev.cpu.0.temperature: 30.0C
dev.cpu.0.temperature: 29.8C
dev.cpu.0.temperature: 30.1C
dev.cpu.0.temperature: 29.8C
dev.cpu.0.temperature: 28.2C
dev.cpu.0.temperature: 26.6C
dev.cpu.0.temperature: 25.0C
dev.cpu.0.temperature: 23.2C
dev.cpu.0.temperature: 21.6C
dev.cpu.0.temperature: 20.0C
dev.cpu.0.temperature: 19.0C
dev.cpu.0.temperature: 18.8C
dev.cpu.0.temperature: 18.7C
dev.cpu.0.temperature: 18.5C
dev.cpu.0.temperature: 18.3C
dev.cpu.0.temperature: 18.2C
dev.cpu.0.temperature: 18.1C
dev.cpu.0.temperature: 17.8C
dev.cpu.0.temperature: 17.7C
dev.cpu.0.temperature: 17.6C
dev.cpu.0.temperature: 17.5C
dev.cpu.0.temperature: 17.3C
dev.cpu.0.temperature: 15.8C
dev.cpu.0.temperature: 15.6C
dev.cpu.0.temperature: 15.3C
dev.cpu.0.temperature: 14.8C
dev.cpu.0.temperature: 14.6C
dev.cpu.0.temperature: 14.5C
dev.cpu.0.temperature: 14.2C
dev.cpu.0.temperature: 13.8C
dev.cpu.0.temperature: 13.7C
dev.cpu.0.temperature: 13.5C
dev.cpu.0.temperature: 13.2C
dev.cpu.0.temperature: 13.0C
dev.cpu.0.temperature: 12.8C
dev.cpu.0.temperature: 12.6C
dev.cpu.0.temperature: 12.6C
dev.cpu.0.temperature: 12.3C
dev.cpu.0.temperature: 12.3C
dev.cpu.0.temperature: 12.1C
dev.cpu.0.temperature: 12.0C
dev.cpu.0.temperature: 11.8C
dev.cpu.0.temperature: 11.7C
dev.cpu.0.temperature: 11.7C
dev.cpu.0.temperature: 11.5C
dev.cpu.0.temperature: 11.3C
dev.cpu.0.temperature: 11.3C
dev.cpu.0.temperature: 11.2C
dev.cpu.0.temperature: 11.1C
dev.cpu.0.temperature: 11.0C
dev.cpu.0.temperature: 11.0C
dev.cpu.0.temperature: 10.7C
dev.cpu.0.temperature: 10.6C
dev.cpu.0.temperature: 10.6C
dev.cpu.0.temperature: 10.6C
dev.cpu.0.temperature: 10.5C
dev.cpu.0.temperature: 10.5C
dev.cpu.0.temperature: 10.3C
dev.cpu.0.temperature: 10.3C
dev.cpu.0.temperature: 10.2C
dev.cpu.0.temperature: 10.1C
dev.cpu.0.temperature: 10.1C
dev.cpu.0.temperature: 10.1C
dev.cpu.0.temperature: 9.8C
dev.cpu.0.temperature: 9.8C
dev.cpu.0.temperature: 10.1C
dev.cpu.0.temperature: 10.2C
dev.cpu.0.temperature: 9.8C
dev.cpu.0.temperature: 9.7C
dev.cpu.0.temperature: 9.7C
dev.cpu.0.temperature: 9.7C
dev.cpu.0.temperature: 9.5C
dev.cpu.0.temperature: 9.3C
dev.cpu.0.temperature: 9.3C
dev.cpu.0.temperature: 9.2C
dev.cpu.0.temperature: 9.1C
dev.cpu.0.temperature: 9.1C
dev.cpu.0.temperature: 9.0C
dev.cpu.0.temperature: 9.0C
dev.cpu.0.temperature: 9.0C
dev.cpu.0.temperature: 8.8C
dev.cpu.0.temperature: 8.8C
dev.cpu.0.temperature: 8.7C
dev.cpu.0.temperature: 9.5C
dev.cpu.0.temperature: 10.8C
dev.cpu.0.temperature: 11.0C
dev.cpu.0.temperature: 11.0C
dev.cpu.0.temperature: 11.1C
dev.cpu.0.temperature: 11.1C
dev.cpu.0.temperature: 11.2C
dev.cpu.0.temperature: 11.2C
dev.cpu.0.temperature: 11.2C
dev.cpu.0.temperature: 11.2C
dev.cpu.0.temperature: 11.2C
dev.cpu.0.temperature: 10.6C
dev.cpu.0.temperature: 9.8C
dev.cpu.0.temperature: 9.8C
dev.cpu.0.temperature: 9.3C
dev.cpu.0.temperature: 9.3C
dev.cpu.0.temperature: 9.3C
dev.cpu.0.temperature: 9.1C
dev.cpu.0.temperature: 8.8C
dev.cpu.0.temperature: 8.7C
dev.cpu.0.temperature: 8.7C
dev.cpu.0.temperature: 8.7C
dev.cpu.0.temperature: 8.5C
dev.cpu.0.temperature: 8.3C
dev.cpu.0.temperature: 8.2C
dev.cpu.0.temperature: 8.2C
dev.cpu.0.temperature: 8.2C
dev.cpu.0.temperature: 8.2C
dev.cpu.0.temperature: 8.1C
dev.cpu.0.temperature: 8.1C
dev.cpu.0.temperature: 8.1C
dev.cpu.0.temperature: 8.1C
dev.cpu.0.temperature: 8.0C
dev.cpu.0.temperature: 8.0C
dev.cpu.0.temperature: 8.0C
dev.cpu.0.temperature: 7.8C
dev.cpu.0.temperature: 7.8C
dev.cpu.0.temperature: 7.8C
dev.cpu.0.temperature: 7.7C
dev.cpu.0.temperature: 7.7C
dev.cpu.0.temperature: 7.7C
dev.cpu.0.temperature: 7.6C
dev.cpu.0.temperature: 7.6C
dev.cpu.0.temperature: 7.6C
dev.cpu.0.temperature: 7.6C
dev.cpu.0.temperature: 7.6C
dev.cpu.0.temperature: 7.6C
dev.cpu.0.temperature: 7.5C
dev.cpu.0.temperature: 7.5C
dev.cpu.0.temperature: 7.5C
dev.cpu.0.temperature: 7.5C
dev.cpu.0.temperature: 7.5C
dev.cpu.0.temperature: 7.3C
dev.cpu.0.temperature: 7.3C
dev.cpu.0.temperature: 7.3C
dev.cpu.0.temperature: 7.3C
dev.cpu.0.temperature: 7.2C
dev.cpu.0.temperature: 7.2C
dev.cpu.0.temperature: 7.2C
dev.cpu.0.temperature: 7.2C
dev.cpu.0.temperature: 7.2C
dev.cpu.0.temperature: 7.1C
dev.cpu.0.temperature: 7.1C
dev.cpu.0.temperature: 7.1C
dev.cpu.0.temperature: 7.1C
dev.cpu.0.temperature: 7.1C
dev.cpu.0.temperature: 7.1C
dev.cpu.0.temperature: 7.1C
dev.cpu.0.temperature: 7.1C
dev.cpu.0.temperature: 7.1C
dev.cpu.0.temperature: 7.1C
dev.cpu.0.temperature: 7.1C
dev.cpu.0.temperature: 7.0C
dev.cpu.0.temperature: 6.8C
dev.cpu.0.temperature: 6.8C
dev.cpu.0.temperature: 6.8C
dev.cpu.0.temperature: 6.8C
dev.cpu.0.temperature: 7.0C
dev.cpu.0.temperature: 6.8C
dev.cpu.0.temperature: 6.8C
dev.cpu.0.temperature: 6.8C
dev.cpu.0.temperature: 6.8C
dev.cpu.0.temperature: 6.8C
dev.cpu.0.temperature: 6.8C
dev.cpu.0.temperature: 6.7C
dev.cpu.0.temperature: 6.7C
dev.cpu.0.temperature: 6.7C
dev.cpu.0.temperature: 6.7C
dev.cpu.0.temperature: 6.7C
dev.cpu.0.temperature: 6.7C
dev.cpu.0.temperature: 6.7C
dev.cpu.0.temperature: 6.7C
dev.cpu.0.temperature: 6.7C
dev.cpu.0.temperature: 6.7C
dev.cpu.0.temperature: 6.6C
dev.cpu.0.temperature: 6.6C
dev.cpu.0.temperature: 6.6C
dev.cpu.0.temperature: 6.6C
dev.cpu.0.temperature: 6.6C
dev.cpu.0.temperature: 6.6C
dev.cpu.0.temperature: 6.6C
dev.cpu.0.temperature: 6.6C
dev.cpu.0.temperature: 6.6C
dev.cpu.0.temperature: 6.6C
dev.cpu.0.temperature: 6.6C
dev.cpu.0.temperature: 6.6C
dev.cpu.0.temperature: 6.6C
dev.cpu.0.temperature: 6.6C
dev.cpu.0.temperature: 6.6C
dev.cpu.0.temperature: 6.6C
dev.cpu.0.temperature: 6.6C
dev.cpu.0.temperature: 6.5C
dev.cpu.0.temperature: 7.2C
dev.cpu.0.temperature: 8.3C
dev.cpu.0.temperature: 8.7C
dev.cpu.0.temperature: 8.7C
dev.cpu.0.temperature: 8.8C
dev.cpu.0.temperature: 9.0C
dev.cpu.0.temperature: 9.0C
dev.cpu.0.temperature: 9.0C
dev.cpu.0.temperature: 9.1C
dev.cpu.0.temperature: 9.1C
dev.cpu.0.temperature: 9.1C
dev.cpu.0.temperature: 8.5C
dev.cpu.0.temperature: 7.8C
dev.cpu.0.temperature: 8.0C
dev.cpu.0.temperature: 7.7C
dev.cpu.0.temperature: 7.5C
dev.cpu.0.temperature: 7.3C
dev.cpu.0.temperature: 7.3C
dev.cpu.0.temperature: 7.2C
dev.cpu.0.temperature: 7.1C
dev.cpu.0.temperature: 7.1C
dev.cpu.0.temperature: 7.1C
dev.cpu.0.temperature: 6.8C
dev.cpu.0.temperature: 6.8C
dev.cpu.0.temperature: 6.8C
dev.cpu.0.temperature: 6.8C
dev.cpu.0.temperature: 6.8C
dev.cpu.0.temperature: 6.8C
dev.cpu.0.temperature: 7.2C
dev.cpu.0.temperature: 8.7C
dev.cpu.0.temperature: 9.0C
dev.cpu.0.temperature: 9.1C
dev.cpu.0.temperature: 9.1C
dev.cpu.0.temperature: 9.2C
dev.cpu.0.temperature: 9.2C
dev.cpu.0.temperature: 9.3C
dev.cpu.0.temperature: 9.3C
dev.cpu.0.temperature: 9.3C
dev.cpu.0.temperature: 9.3C
dev.cpu.0.temperature: 9.0C
dev.cpu.0.temperature: 8.2C
dev.cpu.0.temperature: 8.1C
dev.cpu.0.temperature: 7.8C
dev.cpu.0.temperature: 7.7C
dev.cpu.0.temperature: 7.5C
dev.cpu.0.temperature: 7.5C
dev.cpu.0.temperature: 7.3C
dev.cpu.0.temperature: 7.2C
dev.cpu.0.temperature: 7.2C
dev.cpu.0.temperature: 7.1C
dev.cpu.0.temperature: 7.0C
dev.cpu.0.temperature: 6.8C
dev.cpu.0.temperature: 6.8C
dev.cpu.0.temperature: 6.8C
dev.cpu.0.temperature: 6.8C
dev.cpu.0.temperature: 6.7C
dev.cpu.0.temperature: 6.7C
dev.cpu.0.temperature: 6.7C
dev.cpu.0.temperature: 6.7C
dev.cpu.0.temperature: 6.7C
dev.cpu.0.temperature: 8.1C
```

[EDIT] I just ran the same 8-core job for 6 minutes, and with `top -I` showing all cores at 100% utilisation, the reported temp never got higher than 33.7C.

[EDIT2] Yes, it's granularity.  I took out the `sleep 0.5` and the progression from 6.5C to 30C was smooth.


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## morbit (Apr 4, 2017)

You are looking at 125W TDP. You are off by 20 degrees at the very least.

On the side note, I'm glad Delta is still around. They offered high CFM fans since forever.


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## Crivens (Apr 4, 2017)

... is someone translating farenheit to celsius two times in a row? That would make some more sense, since beating thermodynamics with a fan makes a lot less sense (as others pointed out already).


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