launch titles; Ys Book I & II soon followed. Super CD-ROM² In 1991, NEC introduced an upgraded version of the CD-ROM² System known as the Super CD-ROM², which updates the BIOS to Version 3.0 and increases buffer RAM from 64 KB to 256 KB. This upgrade was released in several forms: the first was the PC Engine Duo on September 21, a new model of the console with a CD-ROM drive and upgraded BIOS/RAM already built into the system. This was followed by the Super System Card released on October 26, an upgrade for the existing CD-ROM² add-on that serves as a replacement to the original System Card. PC Engine owners who did not already own the original CD-ROM² add-on could instead opt for the Super-CD-ROM² unit, an updated version of the add-on released on December 13, which combines the CD-ROM drive, interface unit and Super System Card into one device. Arcade Card On March 12, 1994, NEC introduced a third upgrade known as the , which increases the amount of onboard RAM of the Super CD-ROM² System to 2MB. This upgrade was released in two models: the Arcade Card Duo, designed for PC Engine consoles already equipped with the Super CD-ROM² System, and the Arcade Card Pro, a model for the original CD-ROM² System that combines the functionalities of the Super System Card and Arcade Card Duo into one. The first games for this add-on were ports of the Neo-Geo fighting games Fatal Fury 2 and Art of Fighting. Ports of World Heroes 2 and Fatal Fury Special were later released for this card, along with several original games released under the Arcade CD-ROM² standard. By this point support for both the TurboGrafx-16 and Turbo Duo was already waning in North America; thus, no North American version of either Arcade Card was produced, though a Japanese Arcade Card can still be used on a North American console through a HuCard converter. Variations Many variations and related products of the PC Engine were released. CoreGrafx The PC Engine CoreGrafx is an updated model of the PC Engine, released in Japan on December 8, 1989. It has the same form factor as the original PC Engine, but it changes the color scheme from white and red to black and blue and replaces the original's radio frequency-output connector with a composite video AV port. It also used a revised CPU, the HuC6280A,