TurboGrafx-CD or CD-ROM² is an add-onn accessory to TurboGrafx that allowed the use of CD-ROMs and not only of HuCards.
Useful info:
TurboGrafx was the first console that used CD-ROM as a media.
Release date: 4 December 1988 in Japan, November 1989 United States
Initial Price: $399.99
Fighting Street and Monster Lair were the TurboGrafx-CD launch titles. Ys Book I & II soon followed.
Super CD-ROM² is an upgraded version of CD-ROM² introduced by NEC in 1991. It updates the BIOS to version 3.0 and increases buffer storage from 64KB to 256KB.
Arcade Card is a third upgrade to CD-ROM² introduced by NEC in 12 March 1994, which increases the amount of RAM to 2MB. Arcade Card released in two versions, one as Arcade Card Duo for the consoles that were already equipped with Super CD-ROM² and Arcade Card Pro for those that they had the original CD-ROM².