Igor's Lab has taken on the task of simulating an RX 7800 XT to see what performance might look like. This was done using AMD's new Radeon Pro W7800 graphics card, with half the memory otherwise occupied. Igor's simulation results and theoretical calculations put this theoretical 7800 XT roughly between an RX 6800 XT and RX 6900 XT, or between Nvidia's competing RTX 4070 and 4070 Ti.
The Radeon Pro W7800 is part of AMD's W7000 series workstation GPUs, featuring its latest RDNA 3 GPU architecture. The GPU sports 70 compute units using AMD's Navi 31 die, with 32GB of memory and a total board power rating of 260W. Due to this, the W7800 is arguably the best current candidate for simulating a theoretical RX 7800 XT. That's because it has a 256-bit memory interface, the same as the rumored RX 7800 XT; disabling half of the VRAM should be a reasonably close stand-in for the future GPU.
Igor provided two different test scenarios. The first involved physically simulating a 7800 XT by artificially disabling half of the memory, leaving the GPU with 16GB of GDDR6 VRAM. The second used theoretical calculations taken from the power efficiency results of the RX 7900 XT. The latter was done to attempt to provide a "more accurate" picture of how an actual RX 7800 XT may perform, since the W7800 is tuned for efficiency rather than performance.
It hopefully goes without saying, but both scenarios are at best an estimate of performance. There are multiple issues, including final clock speeds, core counts, whether the "disabled" VRAM truly mimics a 16GB card, drivers, and more. Igor tested at 1080p, 1440p, and 4K. The "simulated" and "calculated" W7800 results were relatively close, with the simulated results looking similar to an RX 6800 XT while the calculated results look more like an RX 6900 XT. Our GPU benchmarks hierarchy incidentally puts the 6900 XT about 7% ahead of the 6800 XT. Here's the overall 1440p chart:
