Thanks for posting.
Some customers have reported success by disabling Turbo Boost, if that's not working for you, then run a systems diagnostics test by pressing F12 at startup or by running Dell Support Assist, make a note of any errors found, and contact Dell Tech Support. You can contact Tech Support at 1-800-624-9896 or 1-800-288-4410, or you can initiate a chat session http://dell.to/2v4snVm
I am glad that dell official account have finally reply this issue. I have tried to disabling Turbo Boost, but it not works in Windows Creator Update 1703(15063). Simultaneously, it also has throttle in 1607(14393) after 20 minutes game playing. I can confirm that it can not be overheat throttle, because the temperature is always fine.
Disabling Turbo Boost and C-States Control will lose performance and make CPU always working on 2.8 GHz. It will shorten the battery life. Also, according to the Intel Product Specifications, the CPU i7-7700HQ should work fine with Turbo Boost. I don't think change the performance setting in BIOS is a sustainable
Firstly, sorry for my bad english.
I also have the problem. When I use the CPU & dGPU at the same time, my CPU's package TDP goint to be limited about 15W, and CPU frequency drop down bellow 2 Ghz in Windows Creator Update 1703 and 1709.
In the 1607 version of Windows 10, my CPU works perfectly. The package TDP limit is 45W and frequency is good.
It's not a solution, to revert back to 1607, so please fix this issue.