I recently tested out the performance differences between my new 4090 and 3080ti with the Ryzen 5800x3D in my Quest 2.
I am using Gryz's complex benchmark mission to allow others to replicate my test method.
https://www.digitalcombatsimulator.com/en/files/3309507/
I disabled ASW in the oculus debug tool to get a true frame time graph with MSI Afterburner.
I'm running the headset at 120hz and maxed out the render resolution slider
In game, I kept the Pixel Density at 1.0 and always used the High Preset.
Results
Gigabyte Gaming OC 4090
EVGA FTW 3 ULTRA 3080 Ti
The improvement is pretty remarkable for very smooth VR performance. Ignoring the jumps at the end and beginning of the benchmark, the 4090 stays around 75-91 fps while the 3080ti only maxes out around 50 fps. It is a night and day difference. (See more info with MSI Afterburner by opening the .hml file attached)
With ASW enabled and using the VR preset, I rarely ever entered any sort of reprojection.
HardwareMonitoring.hml
