  Energy efficiency of electronic digital processors is primarily limited by
the energy consumption of electronic communication and interconnects. The
industry is almost unanimously pushing towards replacing both long-haul, as
well as local chip interconnects, using optics to drastically increase
efficiency. In this paper, we explore what comes after the successful migration
to optical interconnects, as with this inefficiency solved, the main source of
energy consumption will be electronic digital computing, memory and
electro-optical conversion. Our approach attempts to address all these issues
by introducing efficient all-optical digital computing and memory, which in
turn eliminates the need for electro-optical conversions. Here, we demonstrate
for the first time a scheme to enable general purpose digital data processing
in an integrated form and present our photonic integrated circuit (PIC)
implementation. For this demonstration we implemented a URISC architecture
capable of running any classical piece of software all-optically and present a
comprehensive architectural framework for all-optical computing to go beyond.
