Still experiencing PL1 throttling...

[ciosis]

I've got a Dell XPS 13 9360 w/ an i7-8550U I'm looking to squeeze more performance out of since I've noticed it ran quite sluggishly over the years. Played around a bit with Throttlestop recently to see if I could get it to run at higher sustained clocks for a greater period to time as I noticed it was very prone to thermal throttling, hitting 95C+ under load. I managed to reach the following in undervolting:

Important to note for others in the same situation / laptop: I've downgraded to BIOS version 2.13.0 which is the latest BIOS version to support undervolting, I've tried unlocking undervolting in the newest BIOS with this method (https://brendangreenley.com/undervo...s-to-improve-thermals-battery-life-and-speed/) yet it would only work until I've restarted the laptop even with UEFI Capsule Firmware Updates disabled in BIOS, strange... but this works.

CPU Core: -110.4 mV
CPU Cache: -110.4 mV

Intel GPU: -27.3 mV
iGPU Unslice: -27.3 mV

Beyond these values, the system would become unstable and BSOD shortly after. Just another note to confirm that these are the maximum undervolt values I could reach. Tested with TSBench to confirm my CPU is stable at these listed levels.

Seems it partially helped with the temps, so I went a step further and repasted / applied thermal pads to bring them down. Benefits were only substantially marginal, as running TSBench would cause thermal throttling to still kick in albeit slower than before. Currently waiting for a cooling solution to arrive in the mail along with a different thermal paste with a higher rated heat conductivity.

However, I noticed that while gaming with an eGPU (while engaging thermal throttling), I would see PL1 engage and reduce the PKG Power to approx. 15W (Intel's recommended TDP) severely diminishing performance & framerate. I looked in the TPL menu to lock the MMIO Power Limits which appears to be the equivalent of "Disable and Lock Turbo Power Limits" in previous versions of Throttlestop and adjusted the MSR values under Power Limit controls to around the processor's maximum wattage so that LPPL1 and SPPL2 are the same "high" value, also increased the Turbo Time Limit to 160 to see if it would have any effect (at times the CPU ignores large values) so that theoretically the only limit should be thermal throttling.

I ran several instances consecutively of TSBench on 8 threads / 960M size and after thermal throttling ~10 seconds in PL1 follows at around ~28-38 seconds in which is around the default value for the Turbo Time Limit. PL1 continues to limit PKG Power at a dead set 23W, which changing the LPPL1 and SPPL2 with the MMIO lock box checked cannot solve. Attempted to restart the laptop to no effect.

The strangest thing however is that HWinfo reports that the power levels are unlocked!? So I should be able to set and forget as I please within TPL settings. HWinfo even reports the TPL values set in Throttlestop correctly surprisingly... But I'm not sure if Dell has a backup method of PL throttling that I currently do not know of. Considering the 9360 is already 4+ years old I'd imagine I'd find more detail of it's existence if present.

For the record, I also have:

- The laptop plugged in w/ the original OEM Dell charger included with the laptop so that throttling is minimal.
- iGPU disabled while using the eGPU linked to an external monitor (I know undervolting iGPU holds no effect when docked into eGPU, I manually disable the iGPU to yield greater performance)
- All tests with TSBench / Gaming have been carried out with an eGPU + external monitor attached.

I'm honestly at a loss here, unable to pinpoint the exact underlying cause with limited information avaliable. I know Dell introduced embedded controllers independent of those controllable under TPL in their latest models (11th gen I believe) which unfortunately cannot be fixed with Throttlestop. Is this the same with my older model?

Or could it be that constant thermal throttling causes the PL throttling in a form of domino effect? Also, please do let me know if I misunderstood a setting.

I also manually uninstalled the Intel Dynamic Platform and Tuning Frameworks + blocked them from automatically installing, so not exactly sure what's causing the PL1 throttling either.

Attached are my current settings in Throttlestop along with HWinfo screenshots:

 

[unclewebb]

As far as I know, most Dell 8th Gen laptops use an embedded controller (EC) to force turbo power limits to the CPU. The EC limits are separate from the MSR and MMIO power limits. ThrottleStop has no control of the EC power limits.

 

[ciosis]

As far as I know, most Dell 8th Gen laptops use an embedded controller (EC) to force turbo power limits to the CPU. The EC limits are separate from the MSR and MMIO power limits. ThrottleStop has no control of the EC power limits.

Ah hoped that wasn't it... but unfortunately yep that seems to be the case. Thanks for the help, appreciate it!

On the other hand - I've been doing research in the past day or so and discovered a couple interesting modifications that might apply toward solving this issue.

It seems the only method to address this EC throttling is via manipulating the IMON slope, offset, and prefix via a custom BIOS to get the EC to "believe" it's dealing with a wattage lower than is reality. The main problem arrives in flashing the modded BIOS to the XPS, which is unsurprisingly locked by the flash descriptors.

First attempt seems to stem from here: https://www.reddit.com/r/Dell/comments/a2ksoq
There's been a few reported successful attempts at flashing the custom BIOS on the 9360, albeit requiring considerable effort as it's a WSON package. Quite pleased to find that the 2GT/s limitation imposed by Dell on the NVME and TB3 was finally lifted via such method as outlined in this post here: https://winraid.level1techs.com/t/g...pi-link-speed-to-4-gt-s-on-dell-laptops/35373

Might be worth it to increase eGPU performance as well, including opening up IMON variables for further manipulation.

Realtek Pinmod seems to be possible, yet not well-documented. Considering giving this a try...

Edit: Looks to be possible, much easier than expected as the audio chip is located in the front of the board with a pad connected to pin 5 (https://winraid.level1techs.com/t/guide-unlock-intel-fd-on-dell-latitude-e5450/40466). Glad this is an option!