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Drivers & Software

spieiga
Adept I

ryzen on linux and turbo boost xfr

I have a Ryzen 1700X running (no OC).  In windows, I see clock speeds vary from ~2GHz (idle) to 3.9GHz (full load, 3.4 stock + 400MHz boost + 100MHz XFR).

However, in Debian linux with kernel 4.11 with the ondemand governor, I don't see the same scaling limits.

cat /sys/devices/system/cpu/cpu0/cpufreq/scaling_available_frequencies

3400000 3000000 2200000

Under idle, I see 2.2GHz, but then it maxes out at 3.4GHz.  I never see it boost.

Is Turbo Boost + XFR only a Windows thing right now?

EDIT:

https://www.kernel.org/doc/Documentation/cpu-freq/boost.txt

Unfortunately, I do not have

/sys/devices/system/cpu/cpufreq/boost

so that means the acpi_cpufreq driver thinks the Ryzen does not support boost.  Although, in each individual cpu policy (/sys/devices/system/cpu/cpufreq/policy0), I do see a cpb and it is set to 0.  The cpb is supposed to be for older legacy AMD processors, but I'm wondering if Ryzen still supports cpb, or it has to be the boost file in ../cpufreq

EDIT2:

I tried writing 1 to cpb, but I kept getting an invalid argument error.

Anyway, so it seems that you can't actually rely on the information in /proc and /sys to give you accurate realtime speeds of your clock.

Geekblog: Check if AMD's Turbo Core is working on Linux

This helped me see what the clocks were actually performing at.  Ryzen only boosts certain cores temporarily.  I could see on average the core clocks were >3.4Ghz

However, there should still exist /sys/devices/system/cpu/cpufreq/boost, so I reached out to the acpi-cpufreq developer to see why AMD Ryzen is not being recognized as supporting boost.

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4 Replies
quboid
Journeyman III

Re: ryzen on linux and turbo boost xfr

I have a Ryzen 1800X running Debian Stretch with Buster's 4.12 kernel installed on an Asus Prime B350M-E motherboard. I was suspicious that the CPU wasn't boosting up to the higher clock speeds so I spent a while fiddling about in the BIOS before I found your post that explained why none of the usual reporting methods are telling the truth.

Running the BIOS "OC Tuner" caused the BIOS to overclock the CPU from 3.6GHz to 3.85GHz, but doing so appears to also disable the "Turbo-Core" boost. I only realised this when I couldn't reproduce your cpufreq-aperf results.

Disabling "OC Tuner" (which isn't straightforward since the only other available option is "keep current settings") caused the "maximum" CPU speed to go back to 3.6GHz. This re-enabled boost so cpufreq-aperf now reports CPUs running at over 4GHz.

I've had a lot of trouble finding reliable Ryzen on Linux information, so your post was very useful. Thanks.

Mike.

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brauliobo
Journeyman III

Re: ryzen on linux and turbo boost xfr

same here with ryzen 2500U, any solution found?

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mrs
Adept III

Re: ryzen on linux and turbo boost xfr

I use Ubuntu 18.10 on a "AMD Ryzen 5 2500U with Radeon Vega Mobile Gfx".

Actually, I wonder how to deactivate the turbo boost, because the CPU boosts to 3.5GHz (single-threaded) (and even to 3GHz multi-threaded) but I would like it to stay at its base frequency (2GHz) to leave more headroom to the GPU part of the APU.

With the tool "nmon" you can see the current frequency of core:

single-thread.png

multi-thread.png

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alvir
Journeyman III

Re: ryzen on linux and turbo boost xfr

yes, i have needed to adjust bios settings manually to enable boost and increase maximum clock to 4.2 Ghz.

but, to do not stress the cpu i have installed a good cool n quiet driver, the powernowd.

to check if the maximum clock is working execute:
cpufreq-info

by the way my cpu is the atlhon x4 880k

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