GTA 3 for the NES!

In fact, the segacd can't display anything.
So it use a 256ko ram to draw using its Artithmetic chip (exaclty like in a frame buffer), then, it put the ram on the genesis side and the genesis make a DMA to download all the *framebuffer* in vram and the genesis VDP display.

You may now understand why the segacd is so powerful but not very usefull because it loses +75% of time to DMA'te the picture on the genesis side.