You're out of luck there, I'm afraid: All recent versions of Adobe Premiere Pro CC from 2015.3 onwards no longer support switchable graphics (or will no longer allow you to choose the GPU) – but instead will only use the GPU that's designated in the PC as "primary" (which in every single case is the integrated Intel graphics unless that's disabled in the BIOS/EFI or the discrete GPU is selected as the primary GPGPU device in the discrete GPU manufacturer's control panel). Premiere Pro CC 2015.0 through 2015.2 did allow a manual GPU selection in the Adobe settings, but those versions are now no longer available from Adobe due to the Dolby trademark licensing issues.
In addition, the HD 7970 might now be too old to be supported in the MPE OpenCL renderer in newer versions (since CC 2017); thus, the GPU selection in Adobe will default to the integrated Intel HD Graphics regardless of any settings. If that were true, then any attempt to run Premiere CC 2017 or 2018 with only the HD 7970 enabled would have resulted in the MPE renderer being "permanently" locked to the software-only mode.
Thank you very much for the repply!
I'm so disapointed with this... Can't believe they won't let us do a choice that simple.
On my BIOS the Radeon GPU is set to primary, but Adobe keeps ignoring it. I hope it's not "the end" and that must be a way to force it to look at my main GPU as I do (with love kkk).
Again, thanks for the informations!
must be a way to force it to look at my main GPU
Don't connect anything to the Intel output.