The Sega Virtua Processor was only used in one Sega Genesis game, however that game has a special place because of the little SAMSUNG powered chip inside it.
The actual name of the chip is SSP160x, but it wasn't labeled as such inside the cartridge. Sega instead gave it one of its own part numbers. Basically this chip allowed polygons to be rendered out in a format that was compatible with the Genesis/MegaDrive. The MegaDrive doesn't have a bitmap type display that PCs today use, but it made up the screen in tiles. If you wanted to change a pixel in that tile it was a lot harder than it is today.
So the SVP chip receives commands from the Megadrives main CPU (Motorola 68000) telling it where to draw polygons in a "virtual space". The chip then draws them and puts it in a friendly format so that it can quickly be copied into the Megadrives graphics memory.
This chip ran at 23MHz (apparently) and due to the power of the Megadrive CPU could pump out a very realistic 3D looking game. The SNES with its addon chips (the SuperFX for example) were still very limited by the slow SNES CPU which is why Virtua Racing is a lot more impressive from a 16bit 3D standpoint compared to everything on the SNES.
It actually took me longer to add this than it should have. Firstly Grazvydas "notaz" Ignotas should be thanked for reverse engineering and providing source code for the SVP. There were a few small issues in what I was doing that adding emulation of this chip helped pinpoint, so I'm glad I added it, even if only one game uses it. 