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I have noticed if I leave a render process for an extended period of time, the CPU will get to a high temperature and start buzzing. I always immediately cancel/halt the process and let it cool down before continuing, but I would like to know if modern CPU's automatically adjust their workload to current temperature, and if not, what are common and acceptable temperatures for a CPU when performing a heavy workload (like rendering a video file or an output from a 3D application, or similar intensive tasks)?

My specific CPU is an eight core Intel i7, each core running 950 @ 3.07 GHz.

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  • What do you call a high temperature, and where is it measured? – Volker Siegel Jun 3 '15 at 23:22
  • GIGABYTE EasyTune6, applicable to my specific motherboard. I get readings as high as 78* C – veryRandomMe Jun 3 '15 at 23:23
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    What exactly starts buzzing? It's extremely unlikely the actual CPU is buzzing. I'd have some concern about your CPU cooler fan. As the temperature rises, many motherboards increase the fan speed to increase cooling. It may be the fan is loose or the bearing is wearing out. – DoxyLover Jun 3 '15 at 23:57
  • It is a piezo electric crystal buzzer I think. That is the sound it makes anyways, and it comes in 2-3 second intervals. The fan speed gets up to around 1850 RPM and stays there, even when the CPU gets to over 70* C. It coasts at around 1600-1650 RPM when at ~45* C – veryRandomMe Jun 4 '15 at 0:57
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    Define acceptable or safe. You are not going to melt your CPU or start a fire. If your cooling solution is inadequate, there is a safety cut out that will just halt the machine, this could result in data loss. – Jodrell Jun 4 '15 at 8:06
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I would like to know if modern CPU's automatically adjust their workload to current temperature

The CPU can't adjust its workload - it would be up to the operating system scheduler to do so.

What CPU's can (and will) do is begin to throttle their operating frequencies down when the temperature of the cores gets too high.

From this forum post:

If temperatures increase beyond Hot Scale, then ~ 5c below Tjunction Max, Throttling is activated. The Digital Thermal Sensors (DTS) are used to trigger Intel`s TM1 and TM2 technologies for frequency, multiplier and Vcore Throttling within individual Cores. If Core temperatures increase further to Tjunction Max, then Shutdown occurs.

From this Intel Datasheet for the Core 2 Due (June 2009):

When Thermal Monitor 2 is enabled, and a high temperature situation is detected, the Thermal Control Circuit (TCC) will be activated. The TCC causes the processor to adjust its operating frequency (using the bus multiplier) and input voltage (using the VID signals). This combination of reduced frequency and VID results in a reduction to the processor power consumption.

enter image description here

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  • @VolkerSiegel 'workload' in its definition is the amount of work to be done - this is not being changed, the OS is still trying to do the same amount of stuff. But as the CPU slows down it takes longer to do it. – Tom Carpenter Jun 3 '15 at 23:56
  • Hmm... I see what you mean. Looks like "workload" is used like you say in english, but the german Arbeitslast is normally used as per time. But both are used inconsistently. I'll remove my comment above. – Volker Siegel Jun 4 '15 at 0:06
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The real safe operating temperature is documented in the data sheet of you CPU model - there are some variants o i7 CPUs

But this kind of CPU is pretty good in managing it's own temperature.
It can even run parts of the CPU faster than nominal if heat output allows, and changes the speed then other parts get active, also producing heat.

So, as long as the cooling system (like a fan) works normaly, there is no need to worry about that.

Temperature measurements of a cpu can be taken in different locations, resulting in different values.
Two common measurements are at the CPU case, and at the actual CPU silicon die inside.

For example, a i7 could handle a die temperature of around 100°C or so, and start to throtle down at something like 105°C to 110°C.

For real numbers, see the technical data summary table or datasheet of the CPU you are using:
5th Generation Intel® Core™ i7 Processors - Product Specifications

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Assuming it is the 5550U i7

Max temp is 105c

Source of information

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As others have said, the core temp of an i7 should be able to go up past 100° C and will start to go into throttling if it gets hotter than this, and if it gets dangerously hot should shut down automatically to prevent damage.

The safe temperature of CPUs can vary a lot in general, some bugging out when they go past about 65°C but I think this may be more on older CPUs.

You can however on many motherboards go into the BIOS settings at boot and change the warning temperature threshold - this may be set too low for your particular CPU, for some reason. You may also need to look at the emergency shutdown temp threshold if there's one shown in your particular BIOS.

Also note that your software monitor may be reporting the CPU core temp, whereas the motherboard socket temp may be higher - I have a gigabyte motherboard on my i7 950 at home and I can monitor all of the sensor readings directly in the BIOS (though obviously you won't be able to test under load).

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