# PL1 is locked to 20W on XPS 17 9720 after updating BIOS



## TwistedAndy (Sep 16, 2022)

Hello, 

Yesterday I updated BIOS to 1.10.0 on my Dell XPS 17 9720 with Core i9 12900HK and noticed severe performance issues. The performance under sustained load decreased by 40%.

I did some research and found that the PL1 power limit dropped from 45/55W to 20W. The PL2 limit is the same - 115W.

As a result, the CPU is limited to 20W Total Package Power after a few dozen seconds and drops performance significantly.

Before the update, it was limited to the nominal TDP of 45W (Optimized) and 55W (Ultra Performance)

I've checked power limits both using ThrottleStop and HWiNFO:






I've tried rolling back BIOS to 1.9.0, but it did not help.

Other things I've tried:
- Reset BIOS settings (both Factory and BIOS Defaults)
- Reinstall all the drivers for Intel devices from the Dell website
- Reinstall and uninstall Dell Power Manager app and service
- Change power plans in Windows 11 settings
- Switch the power mode in the Dell Power Manager and BIOS to Optimized and Ultra Performance
- Stop/Start the Intel(R) Dynamic Tuning Technology Telemetry Service
- Loading Windows 11 in the Safe Mode. The issue still persists there as well
- Tried connecting the original Dell 130W power supply to the different port

None of those things didn't help.

Are there some ways to resolve this problem?

Thank you!


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## unclewebb (Sep 16, 2022)

Try checking the MMIO Lock box. That is the limit that is incorrectly set to 20W.


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## TwistedAndy (Sep 16, 2022)

Thank you a lot! For some reason, I missed that option. Now the PL1/PL2 limits are correct:





At the same time, without ThrottleStop, the PL1 is still set to 20W.

Also, I've found another interesting problem. Once I lock the MMIO, the laptop is freezing on the Dell logo after the restart. If I shut it down and turn it on, all works correctly.

It looks like this version of Dell's BIOS is pretty buggy. I've opened a ticket through the Dell support team. Hope, they will fix this problem.


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## unclewebb (Sep 16, 2022)

TwistedAndy said:


> the laptop is freezing on the Dell logo after the restart


Are you using ThrottleStop to undervolt your CPU? Not enough voltage can cause a computer to freeze during a restart. 

If CPU voltage control is not Locked and you are using ThrottleStop to undervolt your CPU, try checking the Sleep Defaults - Cache Ratio and Voltage boxes on the right hand side of the FIVR window. This can sometimes help a buggy restart.


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## TwistedAndy (Sep 17, 2022)

unclewebb said:


> Are you using ThrottleStop to undervolt your CPU? Not enough voltage can cause a computer to freeze during a restart.



Yes, I'm using it to undervolt the CPU as well, but I never had issues with a restart or sleep mode.



unclewebb said:


> If CPU voltage control is not Locked and you are using ThrottleStop to undervolt your CPU, try checking the Sleep Defaults - Cache Ratio and Voltage boxes on the right hand side of the FIVR window. This can sometimes help a buggy restart.



In my case, it didn't work. Also, I've tried to reset all the ThrottleStop settings (including FIVR) and kept only MMIO locked. In this case the issue with the restart is also there.

Surprisingly, there are no issues with shutting the system down and turning it on.

Here are my current TS settings:


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## unclewebb (Sep 17, 2022)

If this problem happens when all of your offset voltages are set to +0.0000 in the monitoring table then I have no explanation why this happens. It is even harder to explain when everything works OK after shutting the system down. 

I cannot remember anyone else ever reporting a similar problem where only locking the MMIO caused a computer to hang while resuming. I guess this means that Dell is not very happy with ThrottleStop's MMIO Lock trick.


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## TwistedAndy (Sep 17, 2022)

I think Dell has broken something in the new BIOS release. As a result, we have an issue with the low PL1 limit and other problems.

I've reported this issue to the Dell support team, they pass it to the engineering team. I hope they will release a fix soon


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## TwistedAndy (Sep 21, 2022)

I have found a workaround for the issue with the system restart. Instead of locking the MMIO, I have enabled the Sync MMIO option:



I'm not entirely sure how the MMIO sync is implemented, but it looks to be working.


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## unclewebb (Sep 21, 2022)

Sync MMIO simply copies the MSR power limits to the MMIO memory location.

That is good news If this trick works for you and keeps your laptop happy without any freezes.

I am guessing that the Dell BIOS is trying to write to this memory location without first checking if this memory is locked. Any software, especially the BIOS, should avoid doing something dumb like that. You should only attempt to write to memory after first checking to make sure that it is not locked.


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## TwistedAndy (Sep 22, 2022)

Yes, it looks like you're right.

During the device turn-on and initialization, BIOS sets the wrong power limits to MMIO.

When MMIO is locked, and I trigger the system restart, the BIOS performs a hybrid restart procedure when some memory contents (including information about MMIO lock) are kept in place.

As a result, during the initialization, the BIOS can't set power limits to MMIO because they are locked, and the laptop halts before Windows boot start.

This also explains why there are no issues if I shut down the device and turn it on again.


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## TwistedAndy (Sep 28, 2022)

Yesterday Dell replaced the motherboard in my device. After the replacement, I launched Windows and got the same 20W PL1.

Also, Windows automatically initiated the BIOS upgrade procedure through Windows update to 1.10.0. All the firmware parts (including EC, ME, Thunderbolt controllers, etc.) were updated during the upgrade. This process took longer than usual.

Right after the BIOS upgrade, I entered the BIOS settings, made a factory reset, and switched power modes from Optimized to Ultra-Performance and again to Optimized. I noticed that fans started to spin faster this time once I selected the Ultra-Performance mode. That was a good sign.

But once I loaded it into Windows, I got the same 20W PL1. I decided to try installing the fresh 22H2 version with all the drivers but without any Dell software (including Power Management service).

After installation, Windows installed a weird update with Dell firmware with version 1.9.0. The laptop BIOS version is still 1.10.0, but I see "System Firmware 1.9.0" in the Device Manager. On the previous Windows installation, that device was called "System Firmware 1.10.0".

The behavior of the PL1 limit was also changed. Now it is more dynamic. Under sustained load, it is settled to 45W, but during burst or combined loads, it changes from 30 to 75W.

*Summary:*

1. It looks like this issue was caused by the configuration issues between BIOS, Windows, and virtual devices like "System Firmware 1.10.0";

2. I don't think drivers cause it, because I've installed the identical versions as I had before;

3. Motherboard replacement might help, but I'm not entirely sure.


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