Draqone :
MOST of the work is done by the CPU.
Many GPUs are GOOD ENOUGH for any possible graphic work.
This means upgrading your GPU might not show ANY improvement because it's the CPU that is holding you back.
Yes, but we're not just talking about 'graphics work' in general here, we're talking specifically about GPU accelerated features in Premiere Pro with a few specific graphics cards in question and tests shows that those GPUs have a significant effect on both playback performance and rendering times.
Here's a video by
Dave Dugdale comparing the
GTX680 to the
GTX980Ti in Premiere Pro:
https://www.youtube.com/watch?v=wtxUpzImJvw
As you can see from the video his upgrade from the GTX680 to the 980Ti had a significant impact on playback performance as well as rendering times. His computer is very similar to my own (inluding the same 8-core i7 5960x CPU)
In my own case I myself did rendering tests (no playback tests though) when I bought my GTX1070 where I rendered the same sequence (loaded with GPU accelerated effects) three times over; the first time using CPU only, the second time with my five year old GTX580 enabled and then the third time with my brand new GTX1070 enabled.
As expected rendering times were
significantly faster with GPU acceleration enabled than when using CPU only, so there is beyond any doubt that with GPU accelerated effects the GPU pulls an enourmous load of the work.
What I did not expect in my test was the five year old GTX580 and the brand new GTX1070 delivering the same results in render times! Now this baffled me given that my upgrade leap (GTX580 to GTX1070) was even bigger than that of Dave Dugdale (GTX680 to GTX980Ti) and other people. Yet both his and other tests shows significant performance gains from a major GPU upgrade like that.
So I can only conclude that my seemingly complete lack of performance gain is a result of the GTX1070 not yet being supported in Premiere Pro. It works perfectly in Premiere Pro (as in not being buggy or crashing) it just seems PP is unable to utilize its superior processing power VS the GTX580 for whatever reason.
So clearly I would have been better off buying a GTX980Ti than GTX1070 for working in Premiere Pro as then I would have actually seen massive performance gains.