An interface operable to request instructions from a data store storing instructions of an application to be processed by a data processor, and operable to receive and transmit said instructions to said data processor, said interface comprising: an input operable to receive said instructions from said data store via at least one input bus; a buffer operable to store said received instructions; an output operable to output said instructions to said data processing apparatus via at least one output bus; a control signal input operable to receive a control signal; and a buffer controller operable to: control said buffer to request an instruction subsequent to a previously received instruction within an instruction stream of said application from said data store in response to detection of no control signal on said control signal input and to detection of available buffer storage capacity; and in response to a control signal received at said control signal input, said controller is operable to control at least one of input and storage of instructions within said interface in order to seek to reduce instruction movement through said input.