Overclocking

Overclocking the Radeon RX 7900 XTX is complicated. Just like on RDNA 2, you can no longer dial in a specific clock frequency, but you're operating with min/max sliders to set a range. While on the AMD reference cards, changing the GPU clock does nothing for performance, or it results in a loss of performance or crashes the card when set too high, on this 3x 8-pin custom design things are slightly different.

Due to the increased power limit, the GPU frequency sliders can actually help. Just like on the reference card, for maximum OC performance you should increase power limit to max (+15%), then find your stable memory clock. Memory overclocking works well, but you have to monitor performance. Once memory becomes unstable, there will be no visual corruption, but performance goes down.

Once you have those two, start undervolting until your card is no longer stable—do not touch GPU clocks at this point. As you reduce the voltage, you'll see clockspeed go up automagically, because there is more power headroom to do so. But at some point you'll hit a wall with the clocks, they simply do not go higher, even though they still are 50 MHz below the "clock limit" slider. This is normal for RDNA 2 / RDNA 3, the "maximum" really seems to be "maximum minus 50 MHz."

At this point increase the max clock slider by 100 MHz, leave the minimum clock slider alone.

Now you can see GPU clocks increasing beyond the previous "wall." Keep reducing voltage until your card becomes unstable. If you hit the frequency wall again, increase max clocks by another 100 MHz.

Done!

Overclocked Performance

Using these clock frequencies, we ran a quick test of Unigine Heaven to evaluate the gains from overclocking.


Actual 3D performance gained from overclocking is 6.7%.

I also did a quick run with Cyberpunk 2077, and the results are impressive.



While the AMD reference RX 7900 XTX was 8% faster than the RTX 4080, the stock Sapphire Nitro+ is 11.9% faster, if you add OC+UV on top, you're getting 21.5%—this looks much closer now to what AMD has promised us.