Ok, I found the solution. I don’t know why it happened, but I use an AMD video card, so I checked on Catalyst and Premiere was locked on Power Saving mode, unlike After Effects which was on High Performance mode. But Premiere is locked in there, so I couldn’t change the settings. This is the solution:
Just rename the “Adobe premiere pro.exe” to anything you like.I renamed it to “Adobe premiere pro CC.exe”. AMD Catalyst will recognize it as a new app, and you can change the power setting to Highperformance at all.
Credits: https://devgurus.amd.com/thread/167905