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vtrac

Member

Registered: 2016-01-28

Posts: 42

Audio codec Realtek doing almost 20W?

I have an XPS 13 (9350). I've noticed that my battery mostly sucks - 3 hours or so at best. Taking a look at powertop, I see this:

The battery reports a discharge rate of 27.6 W
The power consumed was 0.00 J
The estimated remaining time is 1 hours, 18 minutes

Summary: 2783.0 wakeups/second,  0.0 GPU ops/seconds, 0.0 VFS ops/sec and 157.6% CPU use

Power est.              Usage       Events/s    Category       Description
  20.2 W    100.0%                      Device         Audio codec hwC0D0: Realtek
  8.45 W    100.0%                      Device         USB device: usb-device-8087-0a2b
  730 mW     21.6 pkts/s                Device         Network interface: wlan0 (iwlwifi)

As far as I can tell, I don't even have any sound playing. The USB device is my intel wifi card.

Is this normal?  Anyone else seeing 20W out of a audio device?

ewaller

Administrator

From: Pasadena, CA

Registered: 2009-07-13

Posts: 19,791

Re: Audio codec Realtek doing almost 20W?

Well....

<soapbox>First, someone needs to file a bug report upstream to powertop.  Joules measure energy, not power. 
And,  power is not consumed. Power is the rate at which work is done. </soapbox>

Second, battery capacities are measured in either Amp  Hours @ some voltage, or in Watt Hours.   Most batteries(1) are on the order of 4 Amp Hours @ between 11 and 14 V.  Let's call it 48 Watt Hours.   You are not going to be able to draw 28 W for 3 hours from a 48Wh battery.  The numbers don't make sense.

Finally, there is no way the audio codec could be dissipating 20W without melting down.  GPUs and CPUs, maybe.  Extreme care goes into the thermodynamic design of those high dissipation parts -- Heat sinks, heat spreaders, fans, etc...   The audio codec, not so much.  That part may (may) have a thermal resistance as low as 50°C / W to ambient.  This assumes a fairly large surface area on top, and a BGA part with fairly tight thermal coupling to the copper traces on your printed wire board.  Given this optimistic thermal conductivity, you would expect a temperature rise in the audio codec of (20W)(50°C / W) or 1000 °C.  Don't think so -- not by an order of magnitude.

(1) Laptop batteries, that is.  Car batteries are on the order of 40 Amp Hours

Last edited by ewaller (2017-05-04 16:50:22)

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vtrac

Member

Registered: 2016-01-28

Posts: 42

Re: Audio codec Realtek doing almost 20W?

Ha, ok. Thanks.