ATI's "R520" core (coenamed Fudo) is the foundation for a line of DirectX 9.0c 3D accelerator X1000 video cards. It is ATI's first major architectural overhaul since the "R300" core and is highly optimized for Shader Model 3.0. The Radeon X1000 series using the core was introduced on October 5, 2005. ATI has released the successor to the R500 series with the R600 series on May 14, 2007.