A display controller 12 comprises a first display processing core 20 comprising a first input stage 21 operable to read at least one input surface, a first processing stage operable to process one or more input surfaces to generate an output surface, and a first output stage 26 operable to provide an output surface for display to a first display 6, and a second display processing core 40 comprising a second input stage 41 operable to read at least one input surface, a second processing stage operable to process one or more input surfaces to generate an output surface, and a second output stage 46 operable to provide an output surface for display to a second display 8. The display controller 12 also comprises an internal data path 30 for passing pixel data of an output surface from the second display core 40 to the first display core 20.