I wouldn't say too early. There were a fair number of temporarily successful co-processors in that general era of many different sorts; aside from float (and sm

I wouldn't say too early. There were a fair number of temporarily successful co-processors in that general era of many different sorts; aside from float (and smaller markets for FFT chips and boards and some efforts at vector co-processors), the most famous were probably the multimedia coprocessors on the Atari ST and on the Amiga (Jay Miner etc). If that's too late for your tastes, look at the nearly universal support chips for 8080/z80 like DMA. Possibly one could count UART and PIO too. But Moore's Law kept killing them, and eventually it became common wisdom that such was the case, so they faded. Over a long time period, external devices to offload the primary cpu come and go, under different guises, as Ivan Sutherland noticed already in 1968. Intel's 8089 and related may have been partially motivated by the success of IO processors in the mainframe and supercomputer world in the 1960s and later. P.S. Hi Chuck :)