Multichip graphics processing subsystems include at least three distinct graphics devices (e.g., expansion cards) coupled to a high-speed bus (e.g., a PCI Express bus) and operable in a distributed rendering mode. One of the graphics devices provides pixel data to a display device, and at least one of the other graphics devices transfers the pixel data it generates to another of the devices via the bus to be displayed. Where the high-speed bus provides data transfer lanes, allocation of lanes among the graphics devices can be optimized.