Is the CPU in my laptop getting throttled during Prime95?

[phositadc]

I'm running a Sony Vaio Pro 11 with an i5-4200U processor and 4GB ram. The clockspeed of the processor is 1.6 GHz.

I decided to run Prime95 to see what the temperatures in the laptop would get up to. For the first few minutes, it ran at essentially full speed and 100% cpu usage. Temperatures were in the high 60s to low 70s Celsius.

But after 5-10 minutes, cpu usage has dropped to 55-60%, and Task Manager is showing the cpu to be running at only 0.90 GHz. Temperatures remain in the high 60s.

Does this mean the CPU is throttling? True, the Sony Vaio Pro 11 is a tiny laptop with only 1 fan, so it wouldn't be that shocking if it were throttling. However, I'm a little surprised to see it throttling when the temp is only 67-69 C. A Thinkpad X240 that I tested did not throttle even though it got up into the low 80s C.

Any thoughts? Am I incorrect about throttling? I appreciate any feedback. Thanks.

 

[ShintaiDK]

The CPU should not throttle before 100C. And it should be able to turbo way above 1.6Ghz.

Are you using battery or AC power?

 

[Phynaz]

How are you executing prime? If I recall it reduces CPU load over time by default when launch from coretemp I think.

 

[D2ultima]

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You could be. It maybe isn't heat, but power. Those are ultra low voltage CPUs, and while during normal use you probably wouldn't cap it out like that, under sustained usage with lack of power the speed could drop. It happens with my 4800MQ; though to a lesser extent. I'll drop from 3.5GHz constant to 3.3-3.4GHz fluctuating across all my cores when I undervolt my CPU. At stock this doesn't happen of course, but again, yours is a ultra low voltage one.

If you use HWMonitor, you should be able to check in real-time and have a list of maximum power drain from the CPU and max temps to see if anything triggered a thermal downclock. Those can happen in the high 80s sometimes, like 88+ deg celcius.

 

[phositadc]

Thanks for the replies. I did a little more research and it appears that it is settings within the Sony BIOS that control throttling. As far as I can tell, they are not modifiable by the user.

There is an app called Vaio Control Center that has settings for the fan. "Aggressive," "Balanced," and "Silence." I discovered that on Aggressive, CPU throttling kicks in at 80 C. On "Balanced" it kicks in around 70 C. And on "Silence" it kicks in at 60 C.

I also saw that at each of these settings, CPU utilization varied while running Prime95. On Aggressive, it would throttle to about 70-80% CPU usage to keep the temp under 80. On Balanced, it would throttle to ~50% to keep the temp under 70. And on "Silence," it would throttle to ~30% to keep the temp under 60.

So yeah, that seems to be it. Throttling instituted by Sony. Overall I guess it seems reasonable. I generally like to keep my CPU temp under 80 C, so I guess I don't mind it throttling at that point even on Aggressive. I wish cooling were a little bit better, because apparently this laptop cannot run at 100% CPU for more than a minute or two before it gets throttled. But I guess that's the price you pay for having a tiny, relatively quiet laptop.

 

[D2ultima]

Yup! Glad you got it sorted out. I'm not sure about the mobile xxxxU chips, but most of the other mobile intel chips can handle up to I believe 105 degrees before damage is done. If it's not 105, it's between 95 and 105.

And yeah. Small/quiet = bad cooling. It just is; there's no room. But don't worry, I don't think too many instances will see you sticking at 100% constant on all cores.