This paper provides a background and rationale for some of the architecture and design decisions in the cell processor, a processor optimized for compute-intensive and broadband rich media applications, jointly developed by Sony Group, Toshiba, and IBM. The paper discusses some of the challenges microprocessor designers face and provides motivation for performance per transistor as a reasonable first-order metric for design efficiency. Common microarchitectural enhancements relative to this metric are provided. Also alternate architectural choices and some of its limitations are discussed and non-homogeneous SMP as a means to overcome these limitations is proposed.