A graphics hub subsystem for interfacing parallelized graphics processing units (GPUs) with the CPU of a PC-based computing system having a CPU interface module and a PC bus. The PC-based computing system includes system memory for storing software graphics applications, software drivers and graphics libraries, and an operating system (OS), stored in the system memory, and a central processing unit (CPU), for executing the OS, graphics applications, drivers. and graphics libraries. The graphics hub subsystem includes a hardware hub having a hub router for interfacing with the CPU interface module and the GPUs by way of the PC bus, distributing the stream of geometrical data and graphic commands among the GPUs, and transferring pixel data output from one or more of the GPUs during the composition of frames of pixel data corresponding to final images for display on the display surface. The subsystem also includes one or more software hub drivers, stored in the system memory. The CPU interface module provides an interface between one or more software hub drivers and the hardware hub. During system operation, the software hub drivers: (i) control the operation of the hardware hub, (ii) interact with the OS and graphic libraries, and (iii) forward the stream of geometrical data and graphic commands, or a portion thereof, to each GPU over the PC bus.