Radeon R520
The R520 (codenamed Fudo) is a GPU developed by ATI and produced by TSMC. It was the first GPU produced using a 90 nm photolithography process.
The R520 is the foundation for a line of DirectX 9.0c and OpenGL 2.0 3D accelerator X1000 video cards. It is ATI's first major architectural overhaul since the R300 and is highly optimized for Shader Model 3.0. The Radeon X1000 series using the core was introduced on October 5, 2005, and competed primarily against nVidia's GeForce 7000 series. ATI released the successor to the R500 series with the R600 series on May 14, 2007.
ATI does not provide official support for any X1000 series cards for Windows 7.
Read more about Radeon R520: Delay During The Development, Architecture