What was the Xbox 360 graphics processor codenamed?

The Xbox 360 graphics processor was codenamed Xenos.

Xenos was the custom graphics system developed for Microsoft's Xbox 360. ATI Technologies designed the chip before AMD acquired ATI in 2006. Its architecture was unusual for a console of its period because it combined a graphics processing unit with 10 MB of embedded DRAM, called eDRAM, on a separate die.

That eDRAM helped the Xbox 360 perform operations such as multisample anti-aliasing efficiently. The Xenos GPU supported unified shader architecture, allowing shader resources to be allocated flexibly between vertex and pixel work. This was an important design difference from many contemporary PC graphics cards.

Xenos is sometimes confused with Xenon, the codename for the Xbox 360's central processor. Xenon used three PowerPC-derived cores, while Xenos handled graphics. The two names were chosen for different major chips in the same console and are frequently mixed up because they differ by only one letter.