You probably already know that the 3 Pop OS Power Modes (Battery Life, Balanced and High Performance) adjust those power levels. And that affects the laptop’s heat output, which in turn affects how the fans operate. But each mode is also controlling the maximum temperatures that are allowed before those fans start spinning, and how fast they spin to control temps.
It’s quite a complicated little dance.
“When you’re in battery mode, it reduces the throttling point for the CPU, as well as the power limit for the CPU,“ he says.
In this power-saving mode, the power limit gets cut in half, from 20W to 10W for the long-term power limit. And the short-term power limit goes from 30W to 20W.” This means the Intel CPU can still go into its “Boost Mode” and deliver immediate performance and higher clock speeds, only when that’s needed.
Another component that’s part of this power, cooling, and temperature puzzle is something called TCC. That stands for Thermal Control Circuit. Ordinarily, that is set at 88 degrees Celsius, but switching that desktop toggle to Power Saving sets this at 70 degrees Celsius.
“When that happens, the fan does not have to act at all. Battery Mode ought to be completely fanless on the Lemur Pro,” Soller explains.
UNLOCKING MORE POWER
Did you know that there’s an upper level of the laptop’s fan curve that you can’t even access until you activate High-Performance mode?
This certainly changes with the hardware, but on the Lemur Pro, the fan normally won’t go higher than 65%. “High-Performance Mode changes the TCC so it’s set at 95C,” Soller says. “So the CPU can get really hot! Additionally, it raises the long-term power limit of the CPU to 25W, and to 40W for the short-term power limit.”
How does that translate to performance though? System76 measured a CPU performance boost of 18%.
“But the chassis heats up!” Soller warns. So you won’t want to have the system on your lap, and you will want to have it plugged into the wall. And you’ll need to accept those fans will be working hard.
So High-Performance mode is ideal for sustained workloads such as encoding a video or perhaps compiling a new software build or kernel.
I encourage you to listen to the entire interview
because it’s educational and entertaining from start to finish.
NEW FAN MODE INCOMING!?
Here’s some news you may not know about…
In the future, System76 will be introducing user-selectable fan modes into Pop OS. So in addition to those 3 power mode choices, we can look forward to 2 brand new fan modes: COOL and QUIET.
Soller explains that the “Cool” mode will keep the chassis cool to the touch, by running the fans at slightly higher RPMs at lower CPU temperatures. “Quiet” mode will do the opposite for times when silence is paramount: the fans won’t spin up even at higher temperatures (within reason of course – System76 understands that no one wants to fry their hardware).
“Having those two toggles lets somebody choose ‘Do I want to optimize for never having the fan turn on?’ When it’s on the desk, you may want to do that. ‘Or do I want to optimize for the chassis being cool?’
In a nutshell: mix and match to make the laptop more comfortable for what you’re doing. Just an extension of what Linux excels at, which is giving people an abundance of choice!