[SOLVED] Why do my cpu cores have different speeds?

hazel · 08-09-2023, 03:44 AM

I have an Intel 4-core processor. When I look at /proc/cpuinfo, the cores all seem to be running at different speeds. Core 1 is the fastest at 2372 MHz, cores 2 and 4 run at 1332 MHz, and core 3 a little faster at 1416 MHz.

Why does this happen and is it normal

?

smallpond · 08-09-2023, 04:49 AM

If you have power-saving enabled, then the cores are slowed down when not busy. Mine say:

Code:

grep MHz /proc/cpuinfo 
cpu MHz         : 800.646
cpu MHz         : 800.076
cpu MHz         : 800.099
cpu MHz         : 800.033
cpu MHz         : 800.000
cpu MHz         : 800.000
cpu MHz         : 800.202
cpu MHz         : 1800.000

triplum.fm · 08-10-2023, 03:55 AM

Quote:

Originally Posted by hazel

I have an Intel 4-core processor. When I look at /proc/cpuinfo, the cores all seem to be running at different speeds. Core 1 is the fastest at 2372 MHz, cores 2 and 4 run at 1332 MHz, and core 3 a little faster at 1416 MHz.

Why does this happen and is it normal

?

What CPU and what kernel are we talking about?

hazel · 08-10-2023, 05:41 AM

Quote:

Originally Posted by Gialo

What CPU and what kernel are we talking about?

It's one of those system-on-a-chip things called a Bay Trail. When I build gmp in LFS, the configuration script identifies it as a Silvermont.The kernel is the standard Slackware-15 one, 5.15.117.

triplum.fm · 08-10-2023, 06:51 AM

Quote:

Originally Posted by hazel

It's one of those system-on-a-chip things called a Bay Trail. When I build gmp in LFS, the configuration script identifies it as a Silvermont.The kernel is the standard Slackware-15 one, 5.15.117.

I've got kinda the same issue with Intel's SkyLake and CometLake CPUs. When I run cat /proc/cpuinfo, I notice that one core keeps running at a way higher frequency than it should. However, when I run 'cpupower monitor', all cores are running at the correct frequency. I'm thinking it might be because of the 6.1.x kernel.

obobskivich · 08-17-2023, 03:12 PM

Like smallpond said, its dynamic clocks based on workload - it makes many adjustments per second, and /proc/cpuinfo (or similar utilities) are only showing a snapshot. You can encapsulate it into a 'watch' to get a more dynamic view of what is happening - single/multiple cores will 'boost up' if they're doing any work. htop can module cpu frequency as well (I believe via the same interface that cpuinfo is using) in newer versions, which can help visualize load/clocks - bear in mind on many newer Intel CPUs there is also HyperThreading, which will double the total logical processors, and there will be pairs of 'cores' with identical clocks (which are the logical processors 'sharing' a physical core). This is normal/expected behavior, and you can modify it to some extent, both by playing with cpu governors (https://www.kernel.org/doc/html/v4.1...m/cpufreq.html) and/or by going into the system's BIOS and changing power or power saving settings (note that this can have a significant impact on operating temperatures and real power consumption depending on the changes you make, and may not have a significant impact on performance vs defaults).