Why my i7 9750H only has six threads while it's supposed to be twelve

[yabinda]

I accidentally found that my i7 9750H in Dell Precision 7540 only has six threads. I checked with both cup-z and HWiNFO64 and it indeed has only six threads.

Does anyone know what's the problem here?

 

[unclewebb]

Run msconfig, click on the Boot tab and press the Advanced options... button.
Make sure the Number of processors box is not checked.
Press OK, reboot and maybe Windows will find the rest of your missing CPU.

Edit - You might want to also enable Speed Shift Technology in your BIOS. While you are in there, make sure hyper threading is enabled.

 

[rethcirE]

It's definitely in the BIOS as @unclewebb mentioned - https://www.dell.com/support/manual...39a04f-55eb-4eaa-8a61-dc9462b93cee&lang=en-us

 

[yabinda]

Run msconfig, click on the Boot tab and press the Advanced options... button.
Make sure the Number of processors box is not checked.
Press OK, reboot and maybe Windows will find the rest of your missing CPU.

Edit - You might want to also enable Speed Shift Technology in your BIOS. While you are in there, make sure hyper threading is enabled.

Thanks. Problem solved with bios adjustment following your instructions. It's wired as I have never touched anything in the bios before.

A follow-up question is previously the CUP speed was locked at around 4.2 GHz. Now it drops to 3.95 GHz. Any ideas?

 

[unclewebb]

speed was locked at around 4.2 GHz. Now it drops to 3.95 GHz. Any ideas?

Intel CPUs vary their speed based on power consumption and on how many cores are active. When you enable hyper threading, you have increased power consumption. That might have something to do with what you are seeing.

Did you enable Speed Shift in the BIOS yet? If you do you will see SST in green in HWiNFO. Most laptops perform better when this feature is enabled.

 

[yabinda]

Thanks for your reply. Yes, I did enable the speed shit in the BIOS. I also disabled the C states control. Hopefully, it has nothing to do with the speed drop.

 

[unclewebb]

I also disabled the C states control.

That makes a mobile CPU run slower and hotter. Was that your goal?
Do not change something if you do not understand what it does.

 

[yabinda]

That makes a mobile CPU run slower and hotter. Was that your goal?
Do not change something if you do not understand what it does.

Ah, got you! Thank you so much for your advice. Everything backs to normal now.