The SNES had Doom running with a SuperFX 2 coprocessor in 1995. https://www.youtube.com/watch?v=n18tcF4nbqE https://www.youtube.com/watch?v=n18tcF4nbqE The Ga

The SNES had Doom running with a SuperFX 2 coprocessor in 1995. https://www.youtube.com/watch?v=n18tcF4nbqE https://www.youtube.com/watch?v=n18tcF4nbqE The Gameboy had several address banks which allowed for whatever coprocessor you wished to put in, you just DMA out of the address space. I suspect the unit volumes just weren't there to justify the enigineering expense in the Gameboy's case. Coincidentally, the Gameboy game X from 1992 ( https://www.youtube.com/watch?v=AyjU4MtonZM https://www.youtube.com/watch?v=AyjU4MtonZM )was developed by Dylan Cuthbert, who later went on to work on Star Fox and the Super FX chip.