AMD APU boost state not active

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1

According to cpupower, my AMD APU K10 is having boost state supported but not active.

How can I make use of the boost state?

As checked in Windows, CPU speed can reach 4GHz without issues. But under Fedora, it can only reach 3.7GHz.

cpupower frequency-info
analyzing CPU 0:
driver: acpi-cpufreq
CPUs which run at the same hardware frequency: 0
CPUs which need to have their frequency coordinated by software: 0
maximum transition latency: 4.0 us
hardware limits: 1.70 GHz - 3.70 GHz
available frequency steps: 3.70 GHz, 3.50 GHz, 3.00 GHz, 2.40 GHz, 1.70 GHz
available cpufreq governors: conservative ondemand userspace powersave performance schedutil
current policy: frequency should be within 1.70 GHz and 3.70 GHz.
The governor “performance” may decide which speed to use
within this range.
current CPU frequency: 3.70 GHz (asserted by call to hardware)
boost state support:
Supported: yes
Active: no
Boost States: 3
Total States: 8
Pstate-Pb0: 4000MHz (boost state)
Pstate-Pb1: 4000MHz (boost state)
Pstate-Pb2: 4000MHz (boost state)
Pstate-P0: 3700MHz
Pstate-P1: 3500MHz
Pstate-P2: 3000MHz
Pstate-P3: 2400MHz
Pstate-P4: 1700MHz

2

# cpupower frequency-set --governor performance seems to have worked for me.

[/root]# cpupower frequency-set --governor performance
Setting cpu: 0
Setting cpu: 1
[/root]# cpupower frequency-info
analyzing CPU 0:
  driver: acpi-cpufreq
  CPUs which run at the same hardware frequency: 0
  CPUs which need to have their frequency coordinated by software: 0
  maximum transition latency: 4.0 us
  hardware limits: 1.40 GHz - 3.10 GHz
  available frequency steps:  3.10 GHz, 2.80 GHz, 2.50 GHz, 2.20 GHz, 1.80 GHz, 1.40 GHz
  available cpufreq governors: conservative ondemand userspace powersave performance schedutil
  current policy: frequency should be within 1.40 GHz and 3.10 GHz.
                  The governor "performance" may decide which speed to use
                  within this range.
  current CPU frequency: 3.10 GHz (asserted by call to hardware)
  boost state support:
    Supported: yes
    Active: yes
    Boost States: 2
    Total States: 8
    Pstate-Pb0: 3700MHz (boost state)
    Pstate-Pb1: 3400MHz (boost state)
    Pstate-P0:  3100MHz
    Pstate-P1:  2800MHz
    Pstate-P2:  2500MHz
    Pstate-P3:  2200MHz
    Pstate-P4:  1800MHz
    Pstate-P5:  1400MHz

Section 4.1 of this PDF document appears to suggest that certain BIOS settings may be required:

The following are the recommended BIOS configurations for HPC.

  • APM enabled to enable core frequency boost.
  • C6 state enabled to allow boost to Pb0 that can provide up to 1 GHz (OPN dependent) core frequency boost when half of the CUs per die are in halted in C6.
1 Like
3

For BIOS, it is the same setting that Windows can reach 4.0GHz.

For cpupower, I can set governors with out issues, just that my boost state support are:
Supported: yes
Active: no

4

There is also a note that turbostat might be required for an accurate reading:

The frequency in /proc/cpuinfo does not show any effect of boost. The turbostat utility, if in your distribution, can be used to actually read the boosted frequency of CPUs.

Other than that, the only “unusual” thing that I currently have configured on my system that I can think of that might be making a difference is that I’ve disabled the security mitigations (mitigations=off on the kernel command line). I don’t know if that would make the difference, but maybe.

1 Like
5

Adding mitigations=off do not help.

As I recalled, last time I checked about this boost state issue (and no solution found) is well before all those CPU side channel attacks are known…