In case you weren't aware, the PC Engine SuperGrafx is a Japan-only system released in 1989. Intended to combat Sega's powerful Mega Drive console – which arrived in 1988, a year after the original PC Engine had launched in that region – the SuperGrafx offered only minor technological improvements over the standard model.
It had four times the amount of RAM for the main CPU, alongside a second video chip with its own dedicated video RAM. However, only six games were ever released for the console, and plans for a fancy 'Power Console' controller – complete with eight-way joystick, four action buttons, flight yoke, throttle lever, jog dial, LCD panel, LED indicator and numerical keypad – were shelved before production could begin due to the high cost (59,800 Yen / $410 USD) and the poor sales of the SuperGrafx system.
Despite being a commercial failure, the SuperGrafx is home to some decent games, including an utterly fantastic port of Capcom's Ghouls 'n Ghosts.
You can download the core here.