Upper right quadrant would be an 8-bit (or maybe 16-bit) CPU paired with a 3D graphics capable GPU. SNES + the SuperFX chip is the closest example I can think of. Similarly, there is the Genesis/Mega Drive + SVP chip.
I can't name a fully 8-bit machine with a 3d focused graphics chip. Maybe there are arcade boards?
It's stretching the definition of "3D-focused graphics chip", but an early example might be I, Robot. An 8-bit 6809 CPU drives a custom polygon-pushing graphics processor. It's primitive but must've been mind-blowing in 1984.
Mega Drive is probably earliest that was capable of it really, but Namco System 21 and especially Sega Model 1 (1990) were designed with 3d/polygons in mind but have relatively old chips in them. Programming for those things could not have been easy.
I can't name a fully 8-bit machine with a 3d focused graphics chip. Maybe there are arcade boards?