Input/output coprocessor for printing machine

A printing machine for concurrently processing first and second sets of image data, comprising:

• a video processing section for processing the first set of image data, including:
• a first bus for transferring the first set of image data thereacross
• an input apparatus, coupled with said first bus, for transmitting the first set of image data, and
• a first page buffer, coupled with said first bus, for receiving the first set of image data from said input apparatus;
• a fault-tolerant coprocessing section coupled with said video processing section, including:
• a second bus for transferring the second set of image data thereacross,
• a plurality of input/output devices, each of said input/output devices being coupled with said second bus,
• a third bus, coupled with said second bus, for transferring the second set of image data thereacross, said third bus being operable notwithstanding the inoperability of said second bus,
• a second page buffer being coupled with said third bus and adapted to store the second set of image data, said plurality of input/output devices being permitted to communicate among one another when said third bus is inoperative, and
• means for transferring the second set of image data between a selected one of said plurality of input/output devices and said second page buffer concurrent with the first set of image data being processed in said video processing section, said transferring means transferring the second set of image data in response to receiving a signal from said selected one of said plurality of input/output devices.