A PC-based computing system capable of displaying images of 3-D objects during an interactive process between said computing system and a user thereof. The PC-based computing system includes a 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 system also includes an CPU interface module, a PC bus, a graphics processing subsystem interfaced with the CPU interface module by way of the PC bus, and a display surface for displaying said images by graphically displaying frames of pixel data produced by the graphics processing subsystem. The graphics processing subsystem includes a plurality of GPUs arranged in a parallel architecture and operating according to a parallelization mode of operation so that the GPUs support multiple graphics pipelines and process data in a parallel manner. A hardware hub, interfaces with the CPU interface module and the GPUs, by way of the PC bus, and has a hub router for (i) distributing the stream of geometrical data and graphic commands among the GPUs, and (ii) transferring pixel data output from one or more of GPUs during the composition of frames of pixel data corresponding to final images for display on the display surface. The CPU interface module provides an interface between one or more software hub drivers and the hardware hub.