I read all the article, and it seems that the benchmark test was ran with a different version of my board, the 2 GB version. Didn't find anything regarding my issue there, though.
Well, after another try I figured it out (thank God). Basically, Window 8.1 was messing around with the driver.
What I did:
- Installed Windows from scratch after updating the motherboard's BIOS;
- Kept spamming the check for updates in Windows Update (Got 252 updates, yes that much) ;
- After no more update was found, I ran CCleaner to verify the registry and system files;
- Then, installed the driver for my GPU, got it from AMD's website;
- Verified Windows Update again, installed 2 more updates;
- Reinstalled ALL games and video-heavy applications from scratch, no backups.
After all this, the driver started working normally. I believe that what did the trick was to wait for Windows to get all the updates he could, for it seemed that the system was not handling the new drivers very well yet.
So, issue solved, I hope this post will be helpful to anyone facing similar issues with fresh Windows based installations.