The present invention relates generally to an optimized memory architecture for computer systems and, more particularly, to integrated circuits that implement a memory subsystem that is comprised of internal memory and control for external memory. The invention includes one or more shared high-bandwidth memory subsystems, each coupled over a plurality of buses to a display subsystem, a central processing unit (CPU) subsystem, input/output (I/O) buses and other controllers. Additional buffers and multiplexers are used for the subsystems to further optimize system performance.