CPU power states and temperature spikes

i just noticed something really unusual on my brand new (slightly used) ASUS N550JV.

During my first checks in general performance and etc, i noticed that the temperatures were unusually high for a brand new laptop computer (idling at around 80Cº).

My first thought was that there could be a problem in the heat sink placement or the thermal paste, but after a few other trials and errors i came to the following conclusion:

If the maximum processor power state (advanced power options in the control panel) is set to anywhere from 1% to 99%, all temperatures are what is to be expected (40-50 idle, 60ish on load). but if the maximum processor state is set to 100%, then i get 80ish at idle and up to 95Cº at load, which is dangerous indeed.

There seems to be a temperature differente of aroung 20Cº between the 99% power state and the 100% power state. Anyone ever saw something like this happening? Is reapplying the thermal paste still a viable try?

PS: the GPU is unaffected.

Timo

Posted 2014-03-05T01:58:56.197

Reputation: 29

Any setting below 100% disables Turbo Boost. – Ben Voigt – 2014-03-05T05:16:14.953

I thought it may have something to do with it. But even so, is 95Cº normal for turbo boost? should i keep using it or better disable it until i apply some arctic silver paste? thanks! – Timo – 2014-03-05T13:35:35.520

95 may be normal under full load with performance boost, but certainly not when idle. Either you aren't really idle or your idle is broken and not making use of the processor's C states. – psusi – 2014-03-31T15:02:45.350

Answers

The CPU is, by design, performance limited by heat. If you want 100% performance, it will crank as much as it can until it can't go any more. 100C is the absolute max, so 95C is the normal limit. It's not dangerous at all.

Trying to keep the CPU cooler is a losing proposition. First, it requires more power to spin the fan faster. Second, it means the same the change in power consumption will produce a larger sudden change in temperature (because the cooler you are, the harder it is to get rid of heat) which creates unnecessary physical stress in the CPU.

David Schwartz

Posted 2014-03-05T01:58:56.197

Reputation: 58 310

If the cpu is idle though, it's performance state should not matter; it is powered down and not generating any heat. – psusi – 2014-03-31T15:01:52.213

@psusi Even at idle, some heat is generated. The system can reduce the fan RPM to keep the CPU warm even at idle. This has the advantages of saving power, reducing noise, and reducing shock heating if the CPU suddenly jumps up to 100% usage. – David Schwartz – 2014-04-04T01:01:27.167

If you mean on average, then yes since there is always some activity waking up the cpu, but during the time when it is actually idle, if it is functioning properly, it is totally powered off and thus generating no heat. While it isn't going to get down to 25C, it should be well below 80. Come to think of it, my cpu ( sandybridge quad core 3.4 Ghz ( 4.3 turbo ) 2500K unlocked and slightly overclocked ) does idle at around 30-32 C, which is getting pretty close to 25. – psusi – 2014-04-04T13:57:36.620

It is certainly not normal if the system is idle. When idle, turbo boost should not be activated. Instead the cpu frequency should be lowered. Even if it is at full performance, when idle the cpu has C states to save power when there is no work to be done. The deepest of those that Intel cpus support is C6, wherein the cpu is entirely powered down. Thus there should be very little heat when idle. It sounds like both of these mechanisms are broken on your laptop. Make sure you have all of the chipset drivers installed from the manufacturer.

psusi

Posted 2014-03-05T01:58:56.197

Reputation: 7 195