cpu not going into C7 when idle

[damndarn]

As the picture shows, all the E cores got stuck in C6 state while the two P cores are running ~20% when idle.
Is it normal for 12th gen cpus? Is there a fix from TS?

 

[Shrek]

What Enabling C6/C7 Low-Power States Do on the Core i7-4770K Haswell CPU - Legit Reviews

"...sadly most motherboard vendors have chosen to disable C6/C7 by default in the BIOS as there are simply too many old or low-cost power supplies on the market that don’t support the power-saving feature."

I don't know if this is still true.

 

[P4-630]

..sadly most motherboard vendors have chosen to disable C6/C7 by default in the BIOS as there are simply too many old or low-cost power supplies on the market that don’t support the power-saving feature."

It's a laptop?

 

[Shrek]

Good point, I missed that.

 

[unclewebb]

@damndarn

Can you use HWiNFO to double check? Does it also report that your E cores are not entering core C7?

I do not have any 12th Gen desktop or mobile hardware or any documentation for development purposes. It looks like the ThrottleStop C States window is reporting things correctly. I do not have anything to compare to so I do not know if 12th Gen E cores not being able to enter C7 is normal or not. It might be a BIOS issue.

It does not seem to be interfering with the CPU package entering package C8 so E cores only entering a maximum of core C6 might just be the way it is with 12th Gen U CPUs.

 

[damndarn]

@damndarn

Can you use HWiNFO to double check? Does it also report that your E cores are not entering core C7?

I do not have any 12th Gen desktop or mobile hardware or any documentation for development purposes. It looks like the ThrottleStop C States window is reporting things correctly. I do not have anything to compare to so I do not know if 12th Gen E cores not being able to enter C7 is normal or not. It might be a BIOS issue.

It does not seem to be interfering with the CPU package entering package C8 so E cores only entering a maximum of core C6 might just be the way it is with 12th Gen U CPUs.

It looks like the so-called efficiency cores can only get into C6 state?

 

[unclewebb]

It looks like the so-called efficiency cores can only get into C6 state?

Yes. That is what your C States data is telling you. Both ThrottleStop and HWiNFO are showing the same thing.

No idea why this is happening. Try to find a different laptop model that you can test that also has a 1255U CPU. Maybe all of these CPUs are like this for some reason that I am not aware of. Intel might have decided to disable C7 in the E cores to fix or hide some bug that they found.

Is there a fix from TS?

This is not a ThrottleStop problem. You cannot use ThrottleStop to fix this problem.

There is not a huge difference between core C6 and core C7 so I would not lose too much sleep over this issue.

Open up a Command Prompt window and enter the command,
powercfg /a

Does your computer support the S0 state? This one is also known as modern standby. I am mostly just curious but the two issues might be related.

 

[Deleted member 57642]

Isn't that normal for the U model (Ultra low power CPU / Mobile power efficient)!?

Here's the description and dependencies for each C state package:

Package C-States - 001 - ID:655258 | 12th Generation Intel® Core™ Processors Datasheet, Volume 1 of 2

edc.intel.com

For Package C6 you have the following Description & Dependencies:

PKG C6

The processor will enter Package C6 when: All IA cores in C6 or deeper + Processor Graphic cores in RC6. The platform components/devices allow proper LTR for entering Package C6. Dependencies: Package C3 + BCLK is off + IMVP9.1 VRs voltage reduction/PSx state is possible.

Of course, as even Intel pointed out:

"The deepest C-state has variance, dependent various parameters such SW and Platform devices."

Which means - you'll need an exact model as yours (same PC + same BIOS) - to get the exact same results (as yours). Different system - can imply different settings (even if it's the same CPU). Did you check your BIOS - to see how your C States are set?

 

[unclewebb]

Package C-States

The package C states are not the problem.

The E cores are not entering the core C7 state. That seems unusual. There is likely a bug somewhere, either in Windows or in the BIOS, that is preventing the E cores from entering core C7.

 

[Deleted member 57642]

The package C states are not the problem.

The E cores are not entering the core C7 state. That seems unusual. There is likely a bug somewhere, either in Windows or in the BIOS, that is preventing the E cores from entering core C7.

Aren't they interconnected? Also, couldn't find a C7 State for 12th Gen:

Can't help but wondering if it's a monitoring bug. I mean, how could he use that system - if it's actually/actively stuck in C6:

"C6 - All clocks are stopped, core state saved,
voltage reduced to 0v"

?!

 

[unclewebb]

couldn't find a C7 State for 12th Gen

The core C7 state exists for the P cores. It is possible that core C7 does not exist for the E cores or the E cores do not report when they are in this C state.

how could he use that system - if it's actually/actively stuck in C6

No one said the CPU is permanently stuck in core C6. The E cores work fine and can go into any available core C state between core C0 and core C6.

 

[Deleted member 57642]

The core C7 state exists for the P cores. It is possible that core C7 does not exist for the E cores or the E cores do not report when they are in this C state.


No one said the CPU is permanently stuck in core C6. The E cores work fine and can go into any available core C state between core C0 and core C6.

Don't have a 12th Gen CPU - so i checked the source for more info (Intel's datasheet on 12th gen). Above attached image - if directly from the source. You can find that info in the Power Management section. That being said and as mentioned above - 12th Generation doesn't have C7 State:

• Full support of ACPI C-states as implemented by the following processor C-states:
  
  • C0, C1, C1E, C6, C8, C10

In their official/public documentation Intel doesn't talk in terms of E Cores or P Cores (or at least - i couldn't find a single reference in either 9th, 10th, 11th or 12th gen datasheet). Supposedly, this info is to basic for the detailed datasheet (if you got that far they expect you to already know that P Cores handle performance or at least demanding tasks - while E Cores are meant for low tasks, power saving and the idle state). On the other hand - checking the datasheet for past 3 generations prior to 12th gen (9th, 10th and 11th) - C7 State is supported by each and everyone of them - both as P-State and C-State.

Here's 9th Gen:

1.3 Power Management Support
1.3.1 Processor Core Power Management
• Full support of ACPI C-states as implemented by the following processor C-states:
— C0, C1, C1E, C3, C6, C7, C8, C9, C10

10th Gen:

1.4 Power Management Support
1.4.1 Processor Core Power Management
• Full support of ACPI C-states as implemented by the following processor C-states:
— C0, C1, C1E, C6, C7, C8, C9, C10

11th Gen:

1.4 Power Management Support
1.4.1 Processor Core Power Management
• Full support of ACPI C-states as implemented by the following processor C-states:
— C0, C1, C1E, C6, C7, C8, C9, C10

I guess, owning an Intel CPU from an older generation - and moving to 12th Gen - makes sense to expect C7 to be there (as it was before). But for some reason (have no idea why - barley find out this myself) Intel decided to change a bit the way C States work - and exclude C7 from 12th gen. Was waiting for someone with a 12 Gen CPU to confirm C7 as unavailable (seems less likely - but even Intel has human employees - so maybe they actually made that mistake 5 out 5 times while writing the datasheet). Or still there?

Based on same datasheet - C6 can also act as the deepest state (handling the higher states) - somehow similar to C7 (in a way - as a replacement). Yet, at same time - was still confused about its description, i mean... C6 was the go to state before shutting down the PC - while now on 12th Gen CPUs can act as a low consumption or idle state. If truly stuck in C6 - that would be problematic (my mistake/misunderstanding) - but if it's a passive go to state - especially while idle - that would make perfect sense for U models (Ultra low power CPU / Mobile power efficient)). Thus, mystery solved (since the OP was wondering why his 12th Gen U model CPU can't go deeper to C7 state / cause there's no such C state and his CPU is working as intended).

Just my 2 cents.

 

[unclewebb]

12th Generation doesn't have C7 State

That is only half true.

The 12th Gen P cores still enter the C7 state. Both ThrottleStop and HWiNFO report this correctly.

If you look in the Software Developer's Manual, the same MSR that keeps track of core C7 residency time has been used for all Intel CPUs since the 2nd Gen Sandy Bridge.
Alder Lake 12th Gen continues to use this same register to record any core C7 activity.

It is possible that the table you posted applies to the 12th Gen E cores.
That table does not apply to the 12th Gen P Cores.
Core C7 works the same as it always has in the P cores.

If there is a difference between the P cores and the E cores, Intel should properly document this in their Software Developer's Manual.