A Reddit user by the name of Jedi95 modified one of the Best GPUs, the RX 7900 XTX to run without a power limit to see how fast the card would go. Thanks to a high-end custom water-cooling setup paired with 10 degrees Celsius coolant temperatures, the power-modded RX 7900 XTX was able to achieve RTX 4090 performance in 3DMark with a very impressive clock speed of 3.33GHz. The only drawback was that the card had to consume nearly 700W to hit this performance target.
The performance achieved by this modified 7900 XTX pushes the card into new territory. In 3DMark Time Spy Extreme, the GPU was able to hit 18,335 points, which exceeds the results of some RTX 4090 cards. For instance, according to PCGamer's RTX 4090 review, it recorded a GPU index score of 16,654 points, which is 10% slower than Jedi95's RX 7900 XTX benchmark result.
This suggests AMD's RX 7900 XTX can jump a performance tier and compete with Nvidia's flagship RTX 4090 (rather than the RTX 4080), at the cost of power consumption. And of course, 3DMark isn't necessarily representative of actual gaming performance.
Power throttling is a very common occurrence on AMD's RX 7900-series cards, with most games being able to hit the maximum power rating on these GPUs. At that point, they'll begin to throttle, or at least not clock as high. This is somewhat different from Nvidia's RTX 40-series GPUs, which often run well below their maximum rated power consumption figures while gaming.
The modified RX 7900 XTX was also able to match the best 7900 XTX Time Spy Extreme benchmark results in the 3DMark browser, competing GPUs that were probably cooled with liquid nitrogen.
The mod Jedi95 used was a "shunt-like" mod that allows the VRM controller to report false power consumption figures to the GPU, thus bypassing AMD's power limitations. This allowed him to effectively run the 7900 XTX without any power limitations whatsoever, since the GPU doesn't know how much power it's actually consuming. According to Jedi95, the mod he used is better than a traditional shunt mod since the power reporting can be controlled with software.
None of this is particularly surprising, as most chips — CPUs, GPUs, and other SOCs — are designed for a particular spot on the voltage and frequency curve. Pushing more voltage through a chip while applying improved cooling can get things running stable, but power scales with frequency and the square of voltage. Adding more of both is a recipe for extreme power use, as shown here.
It's interesting on the one hand to see what AMD's RDNA 3 GPUs can do when power limits are tossed out the window. Running unconstrained, Navi 31 can hit blisteringly high clock speeds of well over 3.3 GHz, yielding significantly higher performance. Based on Jedi95's results, AMD potentially has more than enough headroom to create a theoretical RX 7950 XTX that could compete with the RTX 4090. However, AMD would need to radically increase the chip's power draw to do so.