Just discovered s-tui, a great terminal app for measuring CPU performance/temperature/throttling.

It's really cool and full of useful insights! For example, I discovered that my laptop isn't hitting any more than 3.0 GHz, even though it's rated for 4.0.

Related: any tips on fixing that?



Which machine/chip is it? Some vendors just accept that their machines will be slower for the sake of building something with a desirable CPU into a desirable form factor, even though those two aren't always compatible.

Also, if 4.0 is the top turbo frequency, IDK if there's any general gaurantee it'll get there regularly.

But, if it's old, and it's easy to take apart, it might need to be cleaned up (fans) and have thermal material re-applied.


It's a System76 Galago Pro with a i7-8550U. I don't *think* it's the age—not only is the laptop less than I year old, I've also just replaced the fan.

I think it might be related to thermal throttling on boot. I have full-disk encryption turned on, which seems to make the boot process pretty stressful for the CPU and trigger some sort of throttling. Now, why that's *still* having an effect after the CPU has had plenty of rest after boot, I have no idea…



Just as a guess, because this CPU's stock/base frequency is 1.8GHz, and it can cTDP up to 2.0 at the choice of the OEM (if they put it in something real fat, basically):

4.0GHz is probably an extremely optimistic short-term single-core burst speed.

Does it *never* hit 4 or just not for long or when fully (all cores) loaded?

I haven't looked, but MBP13 or XPS 13 reviews might show more about how this type of CPU tends to do in pretty thin chasses.


It seems to *never* hit anywhere near 4.0 GHz, though I'll need to keep playing around a bit. I've tested it on two different boots (and gotten different performance, which is why I think it might be throttled during boot). The first time, it hit a peak of < 3.1 GHz; the second, it hit a peak of 3.44 GHz. Both times it didn't sustain that peak for long—it could sustain about 2.5 GHz, which seems about right.

I'll look into MBP/XPS 13 numbers; thanks.


I'll poke at my i5-7300u system (Surface Laptop) to see what I can see. That's the previous generation, but same kind of build and cooling.

I'm imagining it's got something to do with stuffing four cores into a 15w heat threshhold, when last year's 15w chips were all duals, but sometimes it just comes down to a bad thermal solution or overly optimistic turbo specs on Intel's part.

I have, in general, yet to read any in-depth reviews of any 8th gen laptops, though.


Thanks. It's not pressing or anything—I don't throw particularly demanding workloads at this computer other than occasionally compiling Rust programs, and speed isn't a huge priority—4.0 GHz is probably overkill anyway. But it would be nice to run this down, for learning purposes if for nothing else.


Yeah, good luck! I'm interested in what anyone else has to say or what you find, because it's something I have thought about but not looked into.

I've just always personally kind of presumed that turbo boost was a lie, and either a CPU was wildly underspecced (Surface 3 can run at max turbo for literally days on end) or completely unattainable (Most MacBook/Pros).


Hmm, interesting: the `cpupower` utility lets me configure my system to use different CPU governors; I can use that to switch from "powersave" to "performance".

It appears that doing so causes my CPU to idle at ~3.8 GHz with ~0.1% utilization instead of at 0.8 GHz (as shown below). It doesn't seem to have *much* impact on peak performance—it's a bit hard to tell, and it's possible that it lets me hit higher than I was getting for a second or two.

All very interesting/odd.

@codesections have you tried setting the cpufreq governer to performance? /sys/devices/system/cpu/cpuN/cpufreq/scaling_governor
Though this will drain battery power faster. You may only want this while on ac power.

According to the README:

"On Intel machines:
Running s-tui as root gives access to the maximum Turbo Boost frequency available to your CPU when stressing all cores. Running without root will display the Turbo Boost available on a single core.

Power read is supported on Intel Core CPUs of the second generation and newer (Sandy Bridge)"

So, did you try running with sudo?

@ohthehugemanatee @sowth

I saw that in the README, so I was running all of the above tests as sudo :)


I did try that! (Though I set it with the cpupower utility rather than by editing the config file directly—thanks for that tip)

It appears that switching to "performance" causes my CPU to idle at ~3.8 GHz with ~0.1% utilization instead of at 0.8 GHz (as shown below). It doesn't seem to have *much* impact on peak performance—it's a bit hard to tell, and it's possible that it lets me hit higher than I was getting for a second or two.

All very interesting/odd.

@codesections in your firat picture you have heat problems. 88/90 degrees is probably your upper limit on your CPU, before your bios starts to throttle. You should be able to check your for the warning limit and it's usually 80-100 degrees.

Grab some new thermal paste (arctic silver) and redo your CPU fan, and clean it out whilst your there. Or get yourself a self contained water cooler instead so under load it stays around 60-70

@ticoombs Interesting. The fan is brand new (installed last week), so it should be very clean. The computer is also under a year old—I take it you're thinking that the paste wasn't very high quality or wasn't applied correctly to begin with?

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