Emulators for older systems very often do this! The older consoles like the NES had a pixel processing unit that generated the picture, you need to emulate it'

Emulators for older systems very often do this! The older consoles like the NES had a pixel processing unit that generated the picture, you need to emulate it's state and interaction with the rest of the system, possibly cycle-by-cycle, which makes it not possible to do on the GPU as a shader or whatever. This is kind of a niche use case for sure but it's interesting.