Since the Turbografx/Duo/PC Engine series of systems can get a bit confusing, I did up a quick guide that should answer most questions. Additionally, the compatibility guide at PCEngineFX is very useful (http://pcenginefx.com/main/nec_compatibility_guide.html).


(actually that is an Arcade Card Pro in the PC Engine above)
In the US, the released systems were the:
-Turbografx-16 (RF out only. An upgrade module for AV was available)
-Turbografx-CD add-on (which includes the IFU of course, and the System 2.0 Card (called the System Card))
-Turboduo (combo cartridge/CD unit with the Super System Card 3.0 upgrade built-in)
-Turbo Express (handheld TG-16. No, you cannot attach the CD unit)
*note: TG-16 controllers are NOT compatible with the Duo or any PC Engine system. You can get a conversion cord, though. Turboduo controllers work on all PC Engine systems and vice-versa.
System BIOS Cards (they are backwards compatible):
-System Card (aka. System 2.0/2.1) -had 64K of RAM
-Super System Card upgrade (aka. System 3.0/3.1) -this added 192KB of RAM for 256KB total
In Japan:
-PC Engine (RF only)
-PC Engine Core Grafx (same thing but with AV-out and a different colour scheme)
-PC Engine Core Grafx II (same thing as the Core Grafx, but with a different colour scheme)
-PC Engine Shuttle (same thing as Core Grafx, but looks way different and has no CD-ROM connector)
-PC Engine GT (same as the Turbo Express; a handheld PC Engine)
-PC Engine LT (sort of like a GT, but with a flip-top screen like the GBA SP. It can only be powered with an AC adapter. You CAN hook it up to a CD-ROM!)
-PC Engine Super Grafx (upgraded PC Engine with more RAM and other improvements. Only 7 games took advantage of this; 5 of which ONLY work on this unit).
-PC Engine CD-ROM2 add-on (came with the IFU or sold seperately. It also came with the System Card 1.0, I believe). You need a special attachment to get this to hook up to the Super Grafx or LT.
-PC Engine Super CD-ROM2 add-on (same as above, but had the Super System Card 3.0 upgrade built-in and looks completely different than the original unit. Matches the Core Grafx II colour scheme)
-PC Engine Duo (combo cartridge/CD unit with the Super System Card 3.0 upgrade built-in)
-PC Engine Duo-R (same as the Duo, but looks different and lacks a headphone jack)
-PC Engine Duo-RX (same as the Duo-R, but has a slightly different colour scheme and comes with a 6-button controller instead of the standard 2-button)
System BIOS Cards:
-System 1.0 -had 64K of RAM. Basically useless except it is required for Altered Beast CD.
-System 2.0 -updated the system BIOS
-System 2.1 -slightly updated the system BIOS again. If you have the 2.0, you probably won't notice a difference.
-Super System 3.0 -had 256KB (1.5MEG) of RAM total. GET AT LEAST THIS!!!!!
-Arcade Card Pro -added over 2MB (17.5MEG) of RAM. Only a few later releases used this. Sapphire is the most well known. All the Neo Geo fighter ports used this as well, and blow away their SNES/Genesis counterparts. The video quality with this blows away anything on the Sega CD.
-Arcade Card Duo -added 2MB (16MEG) of RAM. Can only be used on the Duo line of systems and the Super CD-ROM2 add-on, as they already had 256KB (1.5MEG) RAM built in. The Arcade Card Pro also works on these systems, so this would be a useless card if it wasn't much cheaper than the Pro.
All CD games are region-free. Cartridge games are region locked (and Arcade CD games as a result, as the Arcade Card/cartridge is required for them). There are converters (all expensive) available to play PC Engine games on a Turbografx, but not the other way around.