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Deducing GPU Usage for Final Cut Pro and Compressor by Watts

I wanted to find some supportive evidence that the GPUs were being used for video transcoding, given that Final Cut Pro and Compressor both use nearly all the CPU power. There are not tools I know of to monitor GPU usage (I tried Instruments with no luck).

So I applied a simple logic: use of GPUs should increase the power draw.

Using a Watt’s Up AC power meter @AMAZON, I measured the power draw in watts of the 2013 Mac Pro (8-core 3.3 GHz, D700 GPUs).

MemoryTester 'stress'*: ~ 240 watts (800% CPU usage)

Compressor transcoding to mp4: ~ 195 watts (670% CPU usage)

Final Cut Pro transcoding to mp4: ~ 290 watts (800% CPU usage)

FCP + Unigine Valley render: ~ 380 watts (800% CPU usage)

* Using the MemoryTester 'stress' command of diglloydTools


  • The power draw while using Compressor suggests no GPU usage, since it uses most of the CPUs yet draws notably less power than MemoryTester (which uses no GPU). This makes no sense for Compressor given its nature, but that’s the implication.
  • The Final Cut Pro power draw is significantly higher than with just CPU usage alone, suggesting that GPU usage is employed by FCP.
  • Transcoding in FCP while simultaneously running Unigine Valley render (video fly-thru) becomes slightly jerky, but pushes the power draw up substantially, suggesting that GPU capacity is underutilized by FCP, or simply that some capabilities are inapplicable to transcoding.

There is a lot of hot air coming out the top of the 2013 Mac Pro in the simultaneous FCP + Unigine Valley render!

Fabio I writes:

Why don't simply use iStat Menus to watch GPU current drawing (in Amps) and cores temperature? You could set these values (among others, the same about CPUs for example) on the top screen bar.

MPG: total power draw is one easy number. But this is a very good idea to look at to see if one or two GPUs are being used.

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