The unit had an 8-Bit microprocessor which features integrated bank switching hardware (driving a 21-bit external address bus from a 6502-compatible 16-bit address bus), an integrated general-purpose I/O port, a timer, block transfer instructions, and dedicated move instructions for communicating with the HuC6270A VDC. The 16-bit GPU and video encoder chip allowed the system to produce some incredible looking graphics for the time. The consoles processors were designed and developed by Hudson Soft, and NEC handled the manufacturing.
The TG-16 was a rather unpopular console in the USA due to stiff competition from Sega with the Genesis, and the 8-Bit NES. Games released on the TG-16 tended to fall in the obscure category, and didn't offer a lot of variety in comparison to the established NES and Genesis consoles. However, the TG-16 did offer some stellar titles in the realm of shoot'em ups. Many that stood out beyond what the NES was capable of delivering, or overlooked by Sega. Some were even developed by Hudson Soft directly.
What hurt the sales of the TurboGrafx-16 wasn't the games though. It was Sega's marketing targeting the fact that the main processor for the TG-16 was infact an 8-bit processor. Considering gaming was still a "kids market", most parents didn't know the difference between consoles, other than 16 is a bigger number than 8 and assumed that actually meant the TurboGrafx-16 was an inferior product. On top of that, Nintendo began making its moves into the 16-bit arena with the Super Nintendo. With that, many of the NES loyalists began transitioning over the the next console from Nintendo, completely ignoring the NEC system.
The TurboGrafx-16 did have a CD-ROM add-on. One of the earliest as a matter of fact. It offered TurboGrafx owners the opportunity to experience more in depth games for the console rivaling the depth of Genesis and SNES titles. However, limitations in the console memory impacted the quality. This spawned the TurboDuo in 1991 which fixed a few of these issues.
The TurboGrafx-16 was discontinued in 1995 in North America.