The TurboDuo is the US version of the PCE Duo (the first all-in-one system), the Duo-R is a Japan only cost cutting revision to the original Duo, and the SuperGrafx was an ill-fated attempt at a improved, more powerful system to better compete with the 'real' 16-bit systems (it proved to be unnecessary, as the original system could compete well enough on its own.... in Japan at least). The SG has the same CPU and sound chip but has four times the system ram and adds a second video controller - doubling the video ram, adding a second background plain, and doubling the number of sprites on screen.