1. A multiple GPU (graphics processor unit) graphics system comprising: a plurality of GPUs configured to execute graphics instructions from a computer system, wherein the GPUs are housed in first chassis coupled to the computer system via a serial bus, wherein the computer system is in a second chassis and wherein the first chassis is external to the second chassis and wherein the serial bus comprises a PCI express connection operable to hot-plug to the computer system; a GPU output multiplexer; and a controller unit coupled to the GPUs and the output multiplexer, wherein the controller unit is configured to control the GPUs and the output multiplexer such that the GPUs cooperatively execute the graphics instructions from the computer system and drive a display coupled to the computer system.