Is it a custom chipset, well that depends on a persons perspective, but technically it could be said all gfx cards are.
Custom chips are designed for a system, while off the shelf chips are designed and then put into a system.
So the graphics chips in PS1 & PS2 are custom, but for PS3 & PS4 the distinction becomes blurry but they are effectively off the shelf.
There are no custom 3d graphics chips available for the Amiga.
