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#1 2019-09-13 22:33:33

kimg
Member
Registered: 2019-09-13
Posts: 1

USB DAC - Low CPU load but excessively high CPU frequency

Hello,

I have an Intel Core i7-8565U based computer so intel_pstate driver and the default powersave CPU frequency scaling governor. When playing audio files through an USB DAC the CPU frequency on all threads goes up from ~1000-1500 Mhz to ~4000 Mhz causing a temperature rise of about 7C. When playing the exact same audio files through my motherboard internal sound card (Realtek ALC892) there is no significant CPU frequency change from baseline or subsequent temperature rise. There is almost no CPU load when checking the top utility under both circumstances.

Main software to play the music files is MPD. Have also tried VLC with the same outcome except a little higher CPU load by the VLC process. Only tested ALSA direct output, bypassing PulseAudio.

Also tried two different USB DACs and tested different USB ports, same problem with both devices no matter what port was used. Both DACs have XMOS XU208 USB interface.

Double checked /proc/asound/card*/pcm*p/sub*/hw_params for both DACs and internal sound card to determine that no re-sampling was taking place.

Have not found any faulty behavior of software and hardware when checking the journal.

This seems like excessive CPU utilization, is there anybody out there that can reproduce this issue and/or have suggestions as to what might be the problem?

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