Issue with CPU temp reading from Mobo

[elPapaGoose]

Built a new machine. Everything working great and stress tested. Went to set custom fan profiles and ran into an issue.

 

All my fans are PWM controlled and i'm trying to make a profile where they stay constant untill a certain temp then ramp up quickly after that.

 

Went to test the profile and started the stress test, fans ramp up, then very quickly slow down again.

 

They remain at the low setting while aida64 is running, which is a surprise. Not the end of the world, with my fans at 500-600 rpm, 10mins of aida64 stressing, my hottest core peaked at 83c on a hot day in a closed room. 280mm rads and noctua fans FTW.

 

 

After looking here is the issue:

 

Pwm fans are responding to "CPU" temp reading, not temp core readings (which is normal).

 

The "CPU" temp reading will mostly sit around the temp of my highest core, or thereabouts, but when stressing, after 10 seconds or so the cpu temp reading will drop down again while the temp of the cores continues to climb.

 

When i hit 83c my "CPU" reading was at about 55c or less, so of course the fans are staying at a low rpm.

 

My first thought was that i could just set the fans to ramp up at 50c if the sensor is produving a consisyently low reading, but under normal conditions the sensor is quite accurate (closely mirrors the temp of the cpu cores) and so the fans go crazy everytime i open a program or chrome or what have you. Not the silence i built this thing for.

 

Here is my question:

 

Is this normal behavior for a temp sensor?

 

I understand these things can be out by quite a bit when compared to coretemp, but to be off by 30c for a sustained period of load of 10minutes is wierd to me.

 

It recognises the temp change accurately when the bench starts, so why does the reading go down while temps continue to climb in reality?

 

I can watch this happen with any number of monitoring programs.

 

Does this sound like a faulty sensor?

Anyone else have a similar experience?

Can someone with a similar maximus viii board replicate this?

 

I would love to avoid dealing with asus customer service to get this fixed.

 

Relevant System specs:

Asus maximus viii hero alpha z170, bios 2202

6700k processor

H115i cpu cooler with corsair link.

(All fan are plugged into mobo).

[elPapaGoose]

No replies but i solved it: found helpful info elsewhere.

 

If anyone else has this issue:

Turns out that the bios fan control uses a crappy sensor on the mobo. Fans ramp up when it detects power draw increase, but inaccurate readings result in them ramping down again. Fine for non-overclocked systems with simple cooling, but a bit underwhelming for a mobo this high end.

 

Solution: Download fan software that lets you select what sensor CPU fans respond to (which bios wont let you do).

Now have the fans listening to the CPU's onboard CPU package sensor and performing as desired.

Hope it helps.