FSR, DLSS and Upscaling Explained
Upscaling can reduce the amount of work a GPU performs while still producing an image at the display resolution.
The basic idea
A game can render internally at a lower resolution and reconstruct that image toward the target display resolution. Because fewer pixels are rendered natively, GPU workload can decrease.
FSR and DLSS
AMD FSR and NVIDIA DLSS are different technologies, but both can provide reconstruction or upscaling modes in supported games. Their implementation and image quality vary by game and version.
Quality modes
Modes generally trade internal rendering resolution against image quality and performance. The exact internal resolution and behaviour depend on the technology and game.
When it helps
Upscaling is most useful when the GPU is the main performance limit. If the CPU is limiting frame rate, reducing rendering resolution may produce a smaller improvement.