According to Japanese sources would Nintendo a chip similar to the R770 from the Radeon HD4000 series to use as the gpu for the Wii U. The chip can handle DirectX 10.1 and is capable of four simultaneous screens of image.
Nintendo has not yet commented on the internals of the Wii U, but the Japanese website Game Impress Watch think you know what gpu Nintendo has chosen for the new console during the E3 announced. Nintendo is going to be a chip similar to the R770 from the Radeon HD4000 series to use as a gpu. That seems like outdated hardware, but with a R770 chip, the Wii U both the Xbox 360 and the PlayStation 3 over. The R770 is compatible with DirectX 10.1 and Shader Model 4.1, while the gpu of the Xbox 360 not much further than DirectX 9. The R770 may, in addition, four sd signals at the same time sending out.
That feature does look back at the first rumors about the Wii U appeared. When there was talk of a console with four controllers to be linked could be a sd image would be received from the console. Nintendo has those rumors, however, still denied. According to Nintendo icon Shigeru Miyamoto the Wii U to only one controller handle.