Described herein are electronic gaming machines, and methods of operating electronic gaming machines, configured to enable display of game display data and additional information via common video output. Embodiments of the invention have been particularly developed to enable display of information such as machine diagnostics and bonus games, for example via a secondary display device. While some embodiments will be described herein with particular reference to that application, it will be appreciated that the invention is not limited to such a field of use, and is applicable in broader contexts.