There are three major classes of CD System games: - CD-ROM/CD-ROM2: The "standard" CD system, needs System Card 1/2 - Super CD-ROM2: The "enhanced" CD system, needs Super System Card 3 - Arcade Card CD: Super CD-ROM2 with additional RAM and memory controller, needs an Arcade Card. System Card 1 was, AFAIK, very short-lived and never released outside Japan. The Arcade Card was also not released outside Japan. Using PC-Engine cards on a TurboGrafx system requires either an adapter or a substantial internal modification. Also AFAIK, each card is backward-compatible with games for earlier cards. The Arcade Card comes in two versions - Arcade Card Duo is useful only for Duo systems, while Arcade Card Pro is for the standard PC-Engine. |