NEC TTi Turbo Duo [1990] 

NEC TTi PC Engine Duo [1990] 

This was TTi's TG-16/CD combined unit. It also added more memory for a new format, the Super CD.

An advantage over the TG-CD was its access time. Because the Duo was due to it being one single unit. This system features the "in-built" CD unit for compatibility with then the newest games.