I have a Lenovo T480 with an Intel i7-8650U, which has the notorious problem of dropping itself down to 400 MHz whenever it feels like it, due to power limits. For example, even opening an application that uses the Nvidia GPU (before it even fully loads) causes the machine to throttle down and the fan to slow or stop. Intel Extreme Tuning Utility shows power limiting. Adjusting the power limits lower in XTU doesn’t actually help anything. Neither does limiting the CPU usage to as low as 25% in the Windows Power Settings. (The CPU never goes above 25%, but it still clocks way up to 3.8 GHz.) I have outright disabled using the Nvidia GPU and instead stick to the Intel graphics, which helps but doesn’t totally resolve the problem. This is a system power limit of some kind.
Naturally, I’d rather use my computer at a slower speed for longer, than suddenly landing at 400 MHz. It takes minutes for the Windows start menu to appear when I’m throttled at 400 MHz.
While I can’t disable TurboBoost with XTU, I found that I could disable it with ThrottleStop. With TurboBoost disabled, my CPU never goes above 1.9 GHz. It also never goes lower. No power throttling! I can use my computer all day.
The down side of this is that when I’m doing normal things with spikey loads like web browsing, it would be nice if I could let that CPU go a bit faster. It doesn’t need to go all the way to 3.8 GHz though.
Is there any way to limit the CPU clock speed while in TurboBoost?
Solution:
If you look in the FIVRoption of Throttlestop there is a section to alter the Turbo Boost multiplier limit.
If you reduce the multipliers as far as they will go this will disable Turbo Boost while setting numbers between minimum and maximum will reduce the maximum Turbo Boost and thus heat. You would need to experiment to find suitable values.
As running 4 cores concurrently (which your CPU has) creates more heat than one or two you should consider making the multiplier higher for 1 and 2 than 3 or 4. Changing the turbo limit doesn’t affect stability.
You can also consider under-volting to save more energy and this heat. This is in the middle of the FIVR screen.
You should change “CPU Core”, “CPU cache” and “Intel GPU” to the same offset voltage (for example -100mV each) and test if it is stable both at high CPU use and idle. If set to high you will get a freeze or BSOD in which case power off and try a bit lower (for example -90mv). If it is OK you can increate the under-volt to -110mv and so on until you find a suitable figure for your particular chip. All CPU under-volt differently so you will need to experiment.
As a starting point you could take the figures found in this Lenovo forums thread: T480 throttling and high CPU temps
Undervolting was set to -100mV for the Core, the Cache, and the integrated GPU. The turbo ratio ratio limits were changed from 42/42/39/39 to 40/35/30/25 for 1/2/3/4 cores.
With these settings, the CPU stays at around 68 degrees celsius under moderate game load.