1. A graphics processor, comprising: a raster stage receiving data on primitives to be rasterized, said raster stage generating a plurality of pixel packets for each pixel to be processed, each pixel packet including payload information identifying at least one pixel attribute to be processed and having associated sideband information identifying a sequence of at least one instruction to be executed on said pixel packet; and a programmable Arithmetic Logic Unit (ALU) stage for processing said pixel packets, said ALU stage including at least one ALU, each ALU programmed to have a set of at least one possible scalar arithmetic operation that is performed on an incoming pixel packet having a corresponding current instruction; wherein a sequence of arithmetic operations is performed on said plurality of pixel packets to execute a graphics processing function.