Number 1 - Introduction
There are two modes for the Mercury Playback Engine. The are:
A) Mercury Playback Engine GPU Acceleration
B) Mercury Playback Engine Software Only
To use the Mercury Playback Engine in Adobe Premiere CC 2014, CC, CS6, CS5.5 and CS5 in the GPU Acceleration mode, you need an NVIDIA graphics cards (aka. video cards) with at least 896 megs of video ram and preferably, one of the newer model video cards. I will explain more on this a little later in the article.
When you install Adobe Premiere, and it does not find one of the “certified“ NVidia video cards, the Mercury Playback Engine is set to run in “Software Only” mode, using only the computer’s CPU and not the video card’s GPU.
If you don't have a video card with the NVidia chip set, then Adobe Premiere will run in the "Software Only" mode.
The GPU Acceleration is for accelerated playback, GPU accelerated effects, deinterlacing, blending modes, scaling and rendering the previews and final output.
Adobe Premiere CC 2014, CC, CS6 CS5.5 and CS5 does NOT use the GPU for encoding or decoding the video, only the CPU is used for that.