The TeraDrive (テラドライブ TeraDoraibu) is an IBM PC compatible system with an integrated Mega Drive, developed by Sega and manufactured by IBM in 1991. The TeraDrive allowed for Mega Drive games to be played the same time as the PC section is being used, as it is possible for the Mega Drive and PC hardware to interact with each other.
The system was only released in Japan, as Sega hoped that integrating the then popular Mega Drive console into an IBM PC would attract potential customers wishing to purchase a PC. The system proved unpopular and failed.
Source: Wikipedia, "Sega TeraDrive", available under the CC-BY-SA License.