I was using a AMD Radeon HD 7450 on my editing rig to render H.264 video with the Mercury Playback Engine enabled in Premiere CC (2015.2). I recently upgraded to an AMD RX 480, but even though I'm running the latest drivers and have Mercury Playback Engine enabled, I'm receiving degraded performance.
Is there some setting I need to adapt on either the video card or in Radeon settings or Adobe Premiere Pro CC to achieve equal or the expected heightened rendering performance?
I did at the time, but I since ran into another issue with Premiere endlessly generating peak files, so I upgraded to CC2017, but am getting slow rendering performance again. First, I recommend updating your AMD drivers. Beyond the obvious, I added the RX 480 to the cuda_supported_cards.txt in my Premiere folder.
I don't believe I ever got better performance than my older video card, but I'm also rendering with more effects (like Lumetri color profiles, LUFS normalization, etc.) so it's possible my rig is better now and I just didn't realize it or my rig has always been CPU bound, which is most likely the case.