CPU "throttling" for no apparent reason.

[notcyf]

For some reason my CPU throttles down to 800Mhz for no apparent reason, even when idle. I used HWinfo and the sensors measure normal temperatures(below 50c) and no thermal events are recorded.

However Windows Power is set to never reduce clock speeds either, it's set to High Performance.

I don't know what is going on but it's causing notable slowdown for long periods of time until the clock speed goes back to 4000Mhz and stays there. It only seems to happen when the PC has been idle for a while. It seems to like "lock" the speed in place even when activity is detected, but it should NOT speed down when there's no thermal throttle events and High Performance is enabled.

Could this possibly be a bug in Windows? It only started happening recently.

I'm on a MSI Z170A GAMING M3 and a i5-6600K w/ 16GB DDR-2400Mhz RAM

Edit: There was a new Windows 10 x64 update available and also a new UEFI version, however, this did nothing as the CPU is still stuck to 800Mhz at times.

Edit: Even in UEFI it seems to be throttling with normal temperatures.

[strike]https://i.imgur.com/LLpJpQe.jpg[/strike]


Edit: The above wasn't a cold boot, it could've still been Windows. Restarted my PC a few times cold and it never stated 0.80Ghz again.

 

[notcyf]

Disabling EIST does not work either :/

 

[jay32267]

Processor clock speed generally runs slow when you are idling. This is normal.

Are you finding it is running slow under a heavy load?

 

[notcyf]

It happens under heavy load, when playing games etc.

And no, it's not normal for the CPU to lower clock speed if you run the High Performance profile.


Also if you actually look at the images, you can see that it shouldn't be throttling as the minimum processor state is 100%. Can you please read the topic before replying, so that i don't have to repeat already given information?

I updated the OP, it's evening happening in UEFI.

 

[Peter Martin]

bad cpu?

 

[notcyf]

No, i've had this CPU for about 1.5 years now, and there's not a clear sign that there's something wrong with it. Prime95 runs fine without any issues.



The UEFI speed measure could have been because it wasn't a cold boot, i forgot about that. In a cold boot it always measures the correct frequency.

 

[Barty1884]

I wouldn't worry about the 800MHz showing in the BIOS.... I've seen low clock speeds show there before, but not actually impact anything.

Have you touched C States in the BIOS? I would load defaults in the BIOS first of all, then enable high performance in Windows.


I've seen similar issues before and, IIRC, they've all been on MSI boards. First though would've been a BIOS update, but you've done that.

 

[notcyf]

I already loaded defaults and that didn't do anything. I changed my clock speed from 41 to Auto w/ Turbo disabled and that didn't work, then i re-enabled Intel turbo and the issue just disappeared. I don't know it definitely seems like a motherboard issue/bug.

I also installed the microcode update from https://support.microsoft.com/en-us/help/4100347/intel-microcode-updates-for-windows-10-version-1803-and-windows-server and hopefully it doesn't happen again.

Edit: It's happening again. Is there anything else i can do? :/

 

[notcyf]

According to the ThrottleStop tool "BD PROCHOT" is the reason that my CPU is throttling. I googled what this is and apparently it reduces it's own clock speed when other devices are getting hot.

The only other device that seems to get hot is my Samsung 960 EVO NVME SSD, of which the SSD controller goes around 60-80c, which for a 960 EVO, is normal.

https://i.imgur.com/0KDhr6T.png

Also, even when idle, it won't stop throttling the CPU due to BD Prochot, it is as a matter of fact, still going and the clock speed is stuck at 800Mhz.

 

[notcyf]

Even when running prime95, my PC throttles completely at random, on and off and on and off the BD prochott goes. I read that it could be because of a malfunctioning switch on the motherboard, causing BD Prochot to misfire.

 

[notcyf]

Fixed the issue by flipping the Slow_mode switch a few times and making sure no cables are near it due to staticity.

 

[unclewebb]

The Slow_mode switch on many MSI motherboards has caused this exact same problem for many users. When this switch fails or starts to short out, it will send a PROCHOT signal to the CPU via the BD PROCHOT signal path. This tricks the CPU and forces it to throttle to its minimum speed which is usually 800 MHz. Using ThrottleStop to disable BD PROCHOT will block these signals from getting to the CPU. Only other option is a new board. Not a good situation. There should be a class action lawsuit against MSI to force them to replace all of their defective boards that have this Slow_mode switch problem.

 

[notcyf]

The random nature of the throttling and the fact that flipping the switch back and forth fixed the issue indeed confirms this was the issue. BD PROCHOT shouldn't even be used by desktops, they're meant for laptops and is also in use by the integrated graphics(Intel HD Graphics). It sucks but i think replacing the board would be unnessecary; since REMOVING the short disables slow mode, you can in fact just carefully physically remove the short by removing the switch altogether, but ThrottleStop will work fine for people who don't want to risk completely bricking the mobo.