Effect of turbo power limits and speedstep/speedshift with Throttlestop.

Jeff4321 · April 30, 2021

Hi,

I have a Dell G3 15 laptop with an i7-9750H. Base/Boost clock of 2.6GHz/4.5GHz with a TDP of 45W. During all of my testing, I have kept turbo boost OFF to keep the temps low. Also, no undervolting was applied at any point.

By default, the processor runs at around 75-80C under a heavy load at 2.6GHz (25-30W) for a while and then drops down to around 1.3-1.7GHz. At first, I thought it was thermal throttling. But then I read somewhere that these temps are not high enough for thermal throttling. If it wasnt thermal throttling then maybe it was getting power limit throttled or speedstep/speedshift was keeping the frequency low. So, I tried to test this.

By default, both speedstep and speedshift were turned on in the BIOS. In throttlestop, the speedshift epp value checkbox was unmarked but the green SST along with it indicated that speedshift was on. Speedstep was also turned on in throttlestop. But in TPL section, there was another checkbox for speedshift and it was unmarked.

1. Why are there two different checkboxes for speedshift, one in the starting window and one in TPL section? Also, when both speedshift and speedstep are turned on, which one takes priority over the other and which one should I be using?

In TPL section, PL1 and PL2 were both set to 90W. From what I have learnt, PL2 is the short max power limit at which the processor runs for a while before switching to PL1 when turbo is engaged. If that's the case then PL2 should be a higher value than PL2.

2. In my case, why PL1 and PL2 have the same 90W value? And can these even be responsible for power limit throttling when turbo boost is turned off and the power consumption is much lower than these values as mentioned above?

Now to the testing part. I performed all three of the following steps simultanously. ( I didn't think this through)

I turned both speedstep and speedshift off from the BIOS
I checked the "disable and lock turbo power limits" in the FIVR section
I also disabled PL2 by unchecking the box in the TPL section as I read somewhere that it would prevent any power limit throttling. (This should not have any effect because turbo boost is OFF, both PL1 and PL2 have same value and the actual power being consumed is nowhere near 45W which should be the PL1 value but isn't)

As a result, I experienced no throttling at all. I tested for a long period and the frequency stuck to 2.6GHz and the temperatures went upto 95C. This confirmed that I wasn't getting thermal throttled before because even in the lower 90s, the core frequency didn't drop one bit. So it was either power limit throttling or speedstep/speedshift.

After this, I turned PL2 back on and unchecked the "disable and lock turbo power limit box. And i got the same result. No throttling whatsoever. This confirmed that i wasn't getting power limit throttled either.

The only result I got from this was that either speedstep or speedshift was responsible for the low core frequency as the temps and power were too low for any thermal or power limit throttling.

This is where it gets confusing. When I turned both speedshift and speedstep back ON from the BIOS, the effect stuck around. No throttling and temps were in the 90-95 range. At this point, I have the same default settings as I did at the start of all this but the system was no not behaving as it was before. I turned all of these settings on and off many times from both BIOS and throttlestop. I even removed throttlestop completely and restored factory settings in BIOS. But the condition is similar.

Now I am really confused as to what was the reason of throttling in the first place and why the processor is not throttling anymore. I know that my problem is technically solved but the temps of 90C are very uncomfortable. I would rather have throttling occur than to go beyond the 90C point. If someone can make something of this situation then do le me know.

unclewebb · April 30, 2021

2 hours ago, Jeff4321 said:

Dell G3

Some Dell laptops have a significant throttling problem. When they get hot, instead of Intel thermal throttling taking care of the CPU, Dell decided to create their own throttling method. Dell's method is a disaster. Dell laptops will reduce the turbo power limits to an absurdly low value. This causes some severe power limit throttling. You are lucky if your CPU is still able to run at 1.3 GHz when this happens. Many Dell laptops with this "feature" will run throttled like this for an extended period of time.

This problem has nothing to do with SpeedStep or Speed Shift. On most recent computers, the BIOS will automatically enable Speed Shift Technology when you boot up. If this happens, SST will be shown in green on the main screen of ThrottleStop. When you check the Speed Shift option in the TPL window, this ensures that Speed Shift is enabled and it also sends the Speed Shift Min and Speed Shift Max values to the CPU. If your BIOS is doing this correctly, you do not need to check this box. I never trust anything so I check that box to make sure the CPU Speed Shift variables are setup correctly.

On the main screen is the Speed Shift EPP box. EPP stands for Energy Performance Preference. It allows you to request whether you want maximum performance or maximum power savings. If you are using the Windows Balanced power plan, you do not need to use this option in ThrottleStop. Windows 10 can manage EPP. Open the FIVR window and look at the monitoring table. When you move the Windows power slider in the system tray back and forth, you should see the Speed Shift EPP value change in the monitoring table. This is an easy way to confirm that Windows is managing this setting correctly.

To try to solve Dell's bizarre throttling scheme, you need to remove the DPTF driver and you must block this, take ownership of this, so that Windows cannot reinstall this driver. Do some Google searching about this problem. Here is some more information about this driver and how to get rid of it.

https://bradshacks.com/disable-dptf/#:~:text=In Device Manager%2C find all,for this device" whenever available.