I have MSI Afterburner as my OC software.
Hi.
1)Afterburner has an OC Scanner option. Open AB, click OC Scanner, then click Scan and wait for it to finish. [Took around 35mins for me the last few times I ran it.]
2)When the Scanner is finished, click Apply on the main HUD, then save the profile to one of the numbered buttons(for quick access). After, you click the reset button, then click Revert in OC Scanner.
3)Run benchmark/game on gpu's default. Record, or write down what it gets.
4)Apply the saved profile from the Scanner, click the unlink button(chain link icon), enter a lower value in the Power Limit box, and click Apply.
[This step will need to be repeated until you match your card's performance at default. Use intervals of 5 and 10%, to save some time. For my 1080Ti, I found it at 80% - this doesn't mean it's the same for your card, but it might be a start.]
5)Once you've found a match, save it to a numbered profile. Don't forget to click the Reset button when finished. Done.
Yes, one of the steps above says to lower the power limit, but that's because:
-there's little to gain from just applying a gpu overclock; the built-in boost algorithm monitors gpu operating thermals and power consumption. It doesn't care much for the higher operating thermals and more frequent board power limit breaches that come with OC, and on its own, will dynamically dial things back to its own comfort zone.
-most games and user settings are cpu primary thread bound, and if not that, then software usually follows as the roadblock. If that single thread is already busy trying to send work to the gpu, a gpu OC won't do much.