Coprocessor

In Computer Science the term coprocessor refers to a chip, similar to a computer's central processing unit (CPU), used to offload some of the tasks of the CPU.

The floating point co-processors (FPU) that early intel CPUs relied on worked while the CPU was suspended. Once the FPU had calculated a floating point result, the CPU would be unsuspended.

Other coprocessors, like the "blitter" designed for Commodore's Amiga computers could work in parallel with the CPU. The Amiga was designed to display amazing graphics, and play amazing sound. Amazing graphics and amazing sound required "block transfers" -- the relatively simple transfer of a block of data from one place in memory to another. This was where the name of the blitter came from -- belt. An image, like the background of a window pane, could be held in memory as a sequence of bytes or words, where each byte or word represented a single pixel. Alternatively, it might be held as multiple sequences of bytes and words, where each bit in multiple sequences represented a layer of a pixel in that image.

In either case representing movement on that pane required long and repetive operations over long blocks of data: simple copies of bytes, or the application of binary operations, like OR, ANDs, exclusive ORs, to those long blocks of data.

Because the CPU did not need to access the data bus to talk to memory every single clock cycle the blitter could use those clock cycles for its operations on memory.