CPU clock drops to 400 MHz under high load.

[TD151]

Since a few weeks ago, I noticed massive performance drops while my laptop is under high load. First I thought the issue is caused by the app I'm using but after lots of investigating, the CPU is the one to blame.

When the CPU temperature gets too high (about 85 C) the clock of all cores drops to 400 MHz causing the system to become extremly slow.

Note that:

- The temperature is pretty far from 100 C.

- The fan is not fully ramping up, instead it is more like 50% speed.

- The clock returns to normal in a few seconds after the load is stopped.

About a month ago, I received multiple intel driver related updates, I think this has something to do with the issue. Any suggestions?

[banhien]

@TD151 

That means too hot, CPU has to reduce power to keep it running. One way it can also do: totally shutting the machine down.

Regards.

[TD151]

@Banhien

Back before this issue begun the CPU used to throttle to 1.6 GHz under prolonged load. Now even a 5 minute full load is enough to throttle the CPU so hard to 400MHz (Isn't this too aggressive behavior given that the temperature is pretty far from 100 C?).

I have my system cooling policy set to active and max processor state set to 100%.

Edit: I think the cause is that the gpu is also being highly loaded at the same time, dumping more heat into the heatsink of the CPU and making the fan less effective at keeping it cool.

[TD151 · Accepted solution]

After further testing, turns out the GPU was dumping too much heat in addition to the CPU.

You could reduce GPU max power to help the fan handle the heat dumped without throttling the CPU, or reduce your CPU frequency to help reduce heat.

Also be sure to have enough airflow to help with the cooling.