Overclocking using driver versions 71.89-95.XX or nTune/NVIDIA System Tools is used for both graphics cards simultaneously at the highest stable frequency available for the main card. RivaTuner also allows you to overclock each pair of graphics cards individually. To do this, go to the "Registry" tab (PowerUser), download the RivaTuner.rtd database and set the NVAPIMultiGpuClockControl key to 0 in the "System" section.
After that, when selecting a card in the main window of the program, it is possible to accelerate it specifically. However, it should be noted that the frequency differences of the SLI pair of cards (especially in the GPU frequency) can cause image distortion.
Is it worth buying an already overclocked graphics card?
To avoid the experiments described above, you can always buy a factory overclocked card - say the EVGA FTW3 or MSI Lightning Z - that exceeds the factory clock speeds of the original NVIDIA benchmarks. To put things into perspective, while the 2080 TI is overclocked to 1635MHz by default, the Lightning Z is overclocked to 1770 by default, and thanks to more powerful power supplies and PCBs, you can overclock it even further.
Speed up or reduce the tension
The answer is obvious. Yes, if you remove the manufacturer's restrictions and take control of the frequency and voltage into your own hands, you can achieve better performance. But no one interrupts charging due to heating, increased appetite and the ability to destroy iron. Since this is not possible in the hands of a simple user and without losing the warranty, we have to look for ways to fix what has already been tried to fix before us.
As comparative tests show, the best overclocking of modern Nvidia graphics cards is undervoltage with an increase in memory frequency. We win in performance with much lower energy consumption. And if the owners of models with a good cooling system are not afraid of increased heating, the budget article directly requires such improvements.
As for the final result of factory RTX, in terms of consumption per watt, the graphics card produces an average of 0.3-0.4 frames per second. In "Throttle to the floor" mode, this ratio almost does not change and does not produce more than 0.5 frames. This means that we see a linear increase in productivity with increased consumption.
In the case of undervoltage, the situation is more interesting. The minimum ratio varies between 0.5 and 0.7 images per watt. This means that the temperature has risen significantly. If we imagine the difference between drain and undervoltage as a percentage, it is as follows: up to 15% of the power increases with a decrease in power consumption of up to 20%. Conclusion: overclocking is not only a pointless increase in frequencies and voltages, but also the correct optimization of the work of factory algorithms.