Abstract: A processing device is described that includes a processing cluster having a message management facility and a message processing facility. The message management facility has a first message queue, a second message queue and a queue controller. The message processing facility has a plurality of processing device elements with at least two input ports, and the message processing facility is configured to: receive the selected instruction messages from the message management facility, accept or reject the selected instruction messages, return rejected selected instruction messages as a bounced instruction message to the message management facility, retrieve operand data from an accepted selected instruction message for an input port of a processing device element identified by the selected instruction message, and perform an operation designated to a processing device element once each of its input ports have received operand data.