Overclocking SAPPHIRE Radeon RX 7900 GRE 16GB NITRO+
To overclock the SAPPHIRE NITRO+ RX 7900 GRE 16GB Gaming OC video card we are going to use the built-in performance tuning options in AMD Radeon Software. We were able to increase the power target, the core frequency, and memory. We were not able to increase Voltage, but we could change the fan speed, which wasn’t necessary. We did make sure it could go up to 100% if needed, automatically, but it never needed to.
We were quite limited in our range of options with AMD Adrenalin software tuning. The actual range for the GPU Frequency and Memory was quite restricted, especially on the memory slider. Part of the reason for this may simply be due to the fact that our NITRO+ card is already highly overclocked from SAPPHIRE, but the other side of it may be AMD restricting the overall range. This is especially true on the memory slider, where we could only increase it by 500MHz. 
The default memory frequency is 18Gbps (2250MHz). However, the slider only let us go up to 2316MHz which is just 18.5Gbps or a 500MHz increase. We definitely felt that there was more headroom in the memory itself, but we were simply restricted to great measure in trying to overclock it further. Either we will have to wait for third-party utilizes to allow us to try higher, or AMD is really restricting how far you can push the memory on the 7900 GRE for reasons.
At any rate, we were able to increase the Power Limit by 15%, which definitely helped increase the TDP to give us more headroom on GPU frequency. Unfortunately, with the NITRO+ already being highly overclocked, we also didn’t have a lot of success overclocking the GPU frequency much further. In fact, when we maximized the Max Frequency and Min Frequency sliders, we actually did not see the clock speed increase at all from the setting you see above. 
We have it set at 2600MHz Min Frequency and 2700MHz Max Frequency, and the maximum allowable on the sliders is just 100MHz higher (2700/2800), but we saw absolutely no increase in the frequency from doing that, in fact, it decreased slightly. So our highest overclock is pretty much right here at 2600MHz for the Min Frequency and 2700MHz for the Max Frequency. You can see what that translates to below.
Remember, our SAPPHIRE RX 7900 GRE NITRO+ Gaming OC model is highly overclocked to begin with, with a 9% boost to the gaming clock and a 7% boost to the boost clock, out-of-the-box, compared to reference specs. The boost clock on the NITRO+ is set at 2391MHz by default, and we can see above that this video card is hitting above that most of the time while gaming, which means it is greatly exceeding the game clock of 2052MHz. The average default clock speed is 2411MHz without even overclocking. This means it is right near the boost clock of the 7800 XT by default.
When we overclocked it, with the settings shown above, you can see that the clock speed has increased even more up to the 2560MHz range, and down to 2520MHz at the lowest. The average of this overclock is 2553MHz. At 2553MHz the overclock is just 6% faster than the default clock speed. But keep in mind, this is a lot higher than the base reference AMD specs for clock speed, so if you calculate 2553MHz from the reference GPU boost clock speed of a 7900 GRE, then that’s about a 14% clock speed boost. You are getting a pretty decent boost, but paying for it at $599.
Default on the left, Overclocked on the right. It’s too bad we couldn’t overclock the memory higher with the options available, that might have really helped performance more.