Question regarding CPU temp reporting

[Ian (PassMark)]

No, BurnInTest does not monitor whether the CPU is throttled.

[ACHU]

Thank you. That's very helpful.

Btw, can BurnInTest monitor whether CPU throttled or not?

[Ian (PassMark)]

1 is kind of correct. 2 is incorrect.

To be strictly correct it would read:
Current temperatures are collected every 5 seconds and Maximum, Minimum temperatures are based on these collected temperatures. Maximum, Minimum and Current temperatures are updated every 5 seconds.

[ACHU]

Which one is correct, if I change the interval by changing this "Preferences->Temp / Battery, sample every 5 seconds'?

1. Maximum, Minimum and Current temperatures will be collected every 5 seconds.
2. Current temperatures will be collected every 5 seconds but Maximum and Minimum temperatures are still every 1 second.

[Ian (PassMark)]

=> The max and current are updated at the same time "in the log file". But BurnInTest should have recorded the max at a more frequent rate. Otherwise, the max CPU at event 14 shouldn't go up from 91.0C to 92.0C but the current CPU stays 84C at both event 13 and 14. Correct?

Yes.

Your original log file image shows that Interim periodic logging is set to 10 minutes (Preferences->Logging interval = 10 minutes). So interim results are reported in the log file every 10 minutes, this includes a snapshot of the temperature information at that time.

The current Temperature collection interval is set with the option, Preferences->Temp / Battery, sample every x seconds (which by default is every 1 second). The Maximum and Minimum temperatures are based on these samples (i.e. by default are updated every 1 second).

[orioon]

Most of the time the system vendor enables throttling before reaching 100C, on some system (mostly custom build) this is configurable.
On custom build systems you should expect that throttling won't happen before Intel's limit.
Is this a laptop or a desktop system? Vendor?

Often this is done to reduce temperature issues with other components like the HDD or the chipset.
Even an overheating GPU might cause the CPU to downclock, most typically when they're connected with the same heatpipe (happened to some Dell E6400/E6410 laptops I have access to)

[ACHU]

The max min and current are all updated at the same time.

=> The max and current are updated at the same time "in the log file". But BurnInTest should have recorded the max at a more frequent rate. Otherwise, the max CPU at event 14 shouldn't go up from 91.0C to 92.0C but the current CPU stays 84C at both event 13 and 14. Correct?

[David (PassMark)]

We don't know exactly how Intel implemented the throttling.
It might be they implemented it in such a way to keep the temperature under 100C. That is to say they effectively throttle slightly in advance of 100C.

The max min and current are all updated at the same time.

[ACHU]

Not quite, the CPU max is not monitored. The current CPU temperature is monitored, as mentioned this is configurable in preferences from 1 second upwards. The max CPU temperature is the highest CPU temperature sample from the start of the test to the current reporting time.

=> Take the event log I posted for example. The current CPU temperature is monitored every 10 mins. The current CPU temperature of CPU 0 core 0 stays 84.0C from event 13 to event 14. However, the max CPU temperature of CPU 0 core 0 went up from 91.0C to 92.0C. That means, BurnInTest still kept track of the max CPU during this interim. Can you tell me how often the max CPU temperature is recorded in the software? (As you said, it's not cofigurable. But what's the default?")

It is possible, but I guess there are also other possible explanations.

=> What are the other possibilities?

[Ian (PassMark)]

Here's the scenario. Intel tells us that for certain CPU when its Tj reaches 100C, the CPU will throttle. We ran BurnInTest and the log file showed CPU max is 98C. However, it still throttled. We'd like to know whether it's because BurnInTest didn't record the "ever-happened 100C".

It is possible, but I guess there are also other possible explanations.

[Ian (PassMark)]

Am I right to state this:

"Since the interval of the max CPU temp monitoring can't be configured, the CPU max is monitored every second. If CPU reaches a higher temp within one second, this temperature won't be recorded in the log."

Further to David's comment.

Not quite, the CPU max is not monitored. The current CPU temperature is monitored, as mentioned this is configurable in preferences from 1 second upwards. The max CPU temperature is the highest CPU temperature sample from the start of the test to the current reporting time.

[ACHU]

Here's the scenario. Intel tells us that for certain CPU when its Tj reaches 100C, the CPU will throttle. We ran BurnInTest and the log file showed CPU max is 98C. However, it still throttled. We'd like to know whether it's because BurnInTest didn't record the "ever-happened 100C".

[David (PassMark)]

Any CPU with a heatsink will have a fairly large thermal mass, but have a limited amount of power input during a 1 second period. So is should be near impossible to move the temperature dramatically during a 1 second period.

This doesn't exclude the possibility that some CPUs don't measure their own temperatures very accurately however. e.g. two reads 1ms apart might return a slightly different value.

[ACHU]

Am I right to state this:

"Since the interval of the max CPU temp monitoring can't be configured, the CPU max is monitored every second. If CPU reaches a higher temp within one second, this temperature won't be recorded in the log."

[Ian (PassMark)]

If temperature logging was configured to sample the temperature every 1 second (for example), as per the default, then it is possible that the CPU temperature was higher between the 1st and 2nd temperature samples. e.g. at 1 second it could have been 98C, and at 2 seconds it could have been 98C, but at 1.5 seconds it could have been 100C. The high temperature is based on the BurnInTest samples at 1 second and 2 seconds, i.e. 98C.

In this example, a reading is taken every 1 second and if the temperature sample is hovering around 98C to 100C, then chances are that you are going to get a sample of 100C (unless it really was a one off instantaneous reading of 100C).