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While installing Gentoo on a laptop with an AMD A10-5750M APU using the Gentoo |
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minimal-CD, I was troubled to see the CPU pegged at 3500MHz and consequent |
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thermal cutouts shutting down the laptop. By reducing the number of jobs and |
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using a desktop fan I managed to complete the installation. |
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|
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When I rebooted into my own freshly compiled kernel I noticed the CPU |
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frequency would never go above 2500MHz. Investigating various files under / |
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sys/devices/system/cpu/cpufreq/policy* I was surprised to see there was |
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nothing I could do to either engage any of CPU's boost states, or to increase |
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the frequency above a maximum value of 2500MHz. |
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|
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# cpupower frequency-info |
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analyzing CPU 0: |
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driver: acpi-cpufreq |
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CPUs which run at the same hardware frequency: 0 |
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CPUs which need to have their frequency coordinated by software: 0 |
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maximum transition latency: 4.0 us |
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hardware limits: 1.40 GHz - 2.50 GHz |
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available frequency steps: 2.50 GHz, 2.10 GHz, 1.80 GHz, 1.40 GHz |
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available cpufreq governors: ondemand userspace performance schedutil |
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current policy: frequency should be within 1.40 GHz and 2.50 GHz. |
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The governor "userspace" may decide which speed to use |
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within this range. |
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current CPU frequency: 2.50 GHz (asserted by call to hardware) |
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boost state support: |
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Supported: yes |
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Active: no |
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Boost States: 3 |
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Total States: 8 |
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Pstate-Pb0: 3500MHz (boost state) |
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Pstate-Pb1: 3200MHz (boost state) |
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Pstate-Pb2: 2800MHz (boost state) |
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Pstate-P0: 2500MHz |
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Pstate-P1: 2100MHz |
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Pstate-P2: 1800MHz |
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Pstate-P3: 1400MHz |
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Pstate-P4: 900MHz |
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|
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For example: |
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|
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# echo 3500000 | tee /sys/devices/system/cpu/cpufreq/policy3/scaling_setspeed |
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3500000 |
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# cat /sys/devices/system/cpu/cpufreq/policy3/scaling_setspeed |
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2500000 |
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|
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Or, how about using cpupower? |
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|
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# cpupower frequency-set -g userspace -d 900MHz -u 3500MHz |
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Setting cpu: 0 |
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Setting cpu: 1 |
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Setting cpu: 2 |
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Setting cpu: 3 |
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# cat /sys/devices/system/cpu/cpufreq/policy0/scaling_setspeed |
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2500000 |
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|
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Watching /proc/cpuinfo when compiling never shows the frequency reaching above |
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2500: |
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|
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cpu MHz : 2495.389 |
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cpu MHz : 2495.410 |
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cpu MHz : 2495.389 |
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cpu MHz : 2495.416 |
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I can't think this is some hardcoded BIOS limitation, otherwise how come the |
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minimal-CD was boosting the frequency all the time to the point of shutting |
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down the laptop. Switching governor to 'performance' as the minimal-CD has it |
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set, or to userspace/schedutil has no effect to the maximum frequency the CPU |
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displays. |
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Any ideas how I can activate the boost states on this CPU, or what else I |
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could look into to unlock its potential and speed up my emerge? |
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-- |
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Regards, |
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|
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Mick |
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