The PC Engine is the basic Japanese system. All Japanese PC Engine related systems (except of course the PC-FX, which isn't a PC Engine) play it's HuCards. In the basic family are: PC Engine (white system, only gave an RF Output). Release in Japan on October 30, 1987. It didn't set Japan on fire as you might have expect, but steadily gained in stature, and the games became more and more impressive. It was at the end of March '88 when a virtually arcade perfect port of R-Type was released that everyone finally saw the power of the Engine. Finally, arcade perfection was here, and it paved the way for endless waves of shooters, for which the system is best known. At the time, the tiny HuCards could only hold 2 Megabits of data, so the game had to be released in 2 parts, each containing 4 levels.
The PC Engine was the first console to have a CD-ROM system, in 1989, way before Sega's mega-CD. The first version was a tiny little white system (the same size of a PC Engine), which sat by the side of the PC Engine, attached by an Interface unit, which was all part of a casing which looked like a little grey suitcase. The actual CD-ROM system held no internal memory, so a system card had to be plugged into the card slot of the Engine. The first version, 1.0, didn't last very long, and was quickly replaced by version 2.0. It held 1 MegaBit of RAM, which really wasn't a lot, and to be honest, apart form the huge intros and CD sound, the games were generally outshined by the HuCard games.
In 1991 came the Super CD system, and with it the Duo. They had 2 Megabits of RAM built in, and did not require a system card to play games. To keep up, there was a Super System Card 3.0 released for owners of the old white CD-ROM. Graphics were far better, and certainly upto the level of the card games. In fact, with the huge storage of the CD format, they weren't restricted by the size of the games, and the graphics often looked better then HuCard games.
Finally, there was the Arcade CD card. The Arcade Card Duo (which worked with the Duo and Super CD-ROM systems) featured 16 MegaBits of RAM in addition to the 2 MegaBits inside the systems, giving a total of 18 MegaBits. For owners of the original white CD-ROM, the Arcade Card Pro was released, which simply held 18 MegaBits, and was the more expensive of the two cards.
Unfortunately, by the time the Arcade Card was released, the Engine was well out of the limelight, with the Super Famicom already having been the number one system in Japan for a couple of years, and the Saturn and PlayStation not too far away. Because of this, there weren't that many developers willing to commit, and NEC and Hudson decided to concentrate on converting SNK's Neo-Geo fighting games to the format. While they are admirable conversions with superb animation, this just wasn't what PC Engine owners wanted, besides, you could buy the same games 2nd hand on Neo Cartridge for the same price, and a 2nd hand Neo-Geo cartridge system for not much more than the price of the Arcade card! The huge potential of the Arcade card just wasn't being realised. Apart from the SNK fighting games, most of the games were just Japanese anime-style games, some of which were dual Super/Arcade CD titles (better animation with the Arcade card). Finally, right before the end, (this is not confirmed) at a game show in 1995, Hudson showed a full Arcade CD shooter: Sapphire (GINGA FUKEI DENSETSU SAPPHIRE). They only sold it at the show, which is one of the reasons it's so damned rare and expensive (around £300). Quite simply, it was awesome. Through software, it emulates polygons, warping, morphing, and even has cool lighting! The PC Engine just should not be able to do this sort of stuff!
The PC Engine was also released in the US, with the typically stupid name TurboGrafx-16. It was 're-designed' (looked pretty crappy) and was black. There was a CD-ROM add-on called the Turbo CD, a Super System card released later on, and the PC Engine Duo was renamed the Turbo Duo. The handheld was renamed the Turbo Express. Japanese CDs played on the US systems and vice versa (there were about 3 games which had some problems running), but cards were incompatible. There was an adapter to play Japanese HuCard games on US systems, but it's now quite hard to find.