Linux 5.10.20 Released - Fixes The Erroneous Record-Breaking AMD Clock Frequencies
Written by Michael Larabel in Linux Kernel on 4 March 2021 at 09:38 AM EST. 16 Comments
LINUX KERNEL --
Recent kernel point releases have reported erroneous maximum frequencies on AMD Zen 2 / Zen 3 CPUs in the area of 6GHz+ while now with the latest stable releases that is being fixed.

Linux 5.10.20 LTS is out this morning and it comes with an important fix particularly for AMD Zen 2 / Zen 3 users. The Linux 5.11 fix for that AMD performance regression stemming from the introduction of CPU frequency invariance ended up introducing a regression in the CPU frequency reporting.

For Linux 5.11 and then back-ported to Linux 5.10 LTS was that CPUFreq change and it ended up exposing the entire range of turbo/boost frequencies being reported via /proc/cpuinfo and sysfs. Unfortunately, that entire range is not really accurate and thus a new patch was introduced to ensure only the real maximum CPU frequency is being exposed via these interfaces. This doesn't change the system performance or anything on that front, it's simply about reporting the correct maximum CPU frequency to the user-space tools monitoring /proc/cpuinfo or sysfs.


On recent Linux 5.10 point releases and Linux 5.11 releases up to now, often for the newer AMD processors the kernel would report a maximum frequency in the 6.0~6.5GHz range, which sadly is not feasible with today's processors.

This patch is that fix that is already in Linux 5.12 Git and now in Linux 5.10.20 and will be in the imminent 5.11.3 point release as well.

Update: Linux 5.11.3 is also out now with this fix in place.
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Michael Larabel is the principal author of Phoronix.com and founded the site in 2004 with a focus on enriching the Linux hardware experience. Michael has written more than 20,000 articles covering the state of Linux hardware support, Linux performance, graphics drivers, and other topics. Michael is also the lead developer of the Phoronix Test Suite, Phoromatic, and OpenBenchmarking.org automated benchmarking software. He can be followed via Twitter or contacted via MichaelLarabel.com.

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