Turbo Boost no longer works after laptop wakes up from sleep (m15, possibly other models)

I've noticed the following annoying issue back in my old AW 15 R2 (running 6820HK), then again in a new m15 with i7-8750H on two different motherboards: whenever the laptop is put to sleep and woken up short Turbo Boost no longer works (e.g. the CPU will just stick to the long Turbo Boost TDP of 45W by default even under heavy load).

For the sake of being explicit, since I will copy and paste this this to a Dell support ticket, the following steps reproduce the issue:
1. Restart the PC (to make sure the CPU has been correctly initialised)
2. Run Cinebench 20 and observe the following:
a) Score around the expected maximum
b) CPU initially Turbo Boosting to maximum frequency on all cores as expected
c) CPU package power around the expected maximum initially
All good.
3. Put the PC to sleep and wake it up
4. Run Cinebench 20 and observe the following:
a) score well below the expected maximum / previous score
b) CPU not Turbo Boosting to maximum frequency on all cores as expected under load (or doing so just very briefly)
c) CPU package power not exceeding the TDP (45W for i7-8750H) or doing so very briefly, for 1s maybe

There seems to be a workaround: ensure the PC doesn't sleep but rather hibernates (need to remap the lid close/power button actions as well as timed sleep events in settings).

Still, short Turbo Boost should work correctly after the notebook wakes up from sleep, and I'm sure this has confused many users.
Can people reproduce this issue on their machines? More evidence would be helpful. BTW I tried with and without TS - makes no difference.
A quick google suggested this is likely a BIOS issue whereby some CPU config registers are not set correctly after wakeup so I'm hoping Dell will be able to fix this.

Intel support suggested this is a BIOS issue.

 

Dell PCs have issues with hibernates, it exists on previous gen and affects future generation as well. Disable it and default to sleep mode.

 

Hibernate was indeed broken in AW 15 R2. It's actually somewhat opposite in the m15. Not that sleep is completely broken, but there is a subtle bug, as explained above.

 

Do you observe this issue after a driver update or something? Just use TS and post what C state it idles.

 

So, Dell support have passed this on to a team who will attempt to reproduce. Stay tuned!

 

OK, so Dell have managed to reproduce this although they believe that Turbo Boost no longer working is "normal behaviour". I explained to them why it's not normal and why it should be fixed. Stay tuned

 

Pretty poor response from Dell:

"I already consulted your case with our L3 engineer and he confirmed that the mentioned behaviour is normal. The system is working as designed.
As I wrote before, the Turbo Boost technology is quite complex and affected by many circumstances. So it's quite difficult to say why and how exactly it's affected by the Sleep Mode.

If you are not happy how the computer behaves, you can ask for the full refund."

Just LOL. Frank Azor to the rescue I guess.

 

Ask for Full refund and call it a day. Everything just works at Dell and Nvidia, Doesn't it? Even their A51m going up in flames are normal since end users tax their system too much and game at ultra settings. Thank you Dell for wise words.
Grab something else and call it a day!

 

Grab what, though?

 

Legion Y740 with 8750H and RTX 2060 because of heavy price cuts when 9xxx series are incoming.