The earliest Atari 2600 cartridge that could load games was the Cuttle Cart. This used the Starpath Super Charger method to load games by converting the binary file into an audio signal which the Cuttle Cart would receive and load into its 64KB of RAM. It was very impressive for its time because it could run virtually the entire 2600 library. However, it was slow, every file had to be converted, only one game could be stored in its RAM at a time and the audio connection was not always reliable. (There was a utility to convert binary files on the fly, and when I onwed one I rarely had an issue when a game was corrupted.) Next came the Krokodile Cart, which supported serial transfers and a menu but was not as compatible with as many games. It did come with 512KB of Flash to load games and 32KB of RAM for games that required it.
This Christmas I was extremely fortunate to acquire an Atari 2600 Harmony Cartridge. The Harmony Cartridge is a flash cart that can load games off SD cards (SD Version) or microSD cards (microSD Version). It will work with just about any Atari 2600 game ROM in existence. The Harmony supports SD and microSD cards up to 32GB in size, and has 32KB of Flash and 8KB of RAM for games.
When the Harmony boots, you will see a Ying/Yang symbol for a second, then go to a menu. The Harmony supports folders and can display ten files or folders on a page and twenty four characters of a file or folder name. It has a page number to help keep your place in directories. It will not automatically sort files and folders alphabetically, use Drive Sort for that. You may wish to truncate file names for a more refined cosmetic experience and make a note if they require a controller other than a joystick.
When you select a game, you will see the Ying/Yang logo for a second or three as the game is burnt to the Flash, but it is very quick. Then the game will start as if you had the original cartridge in the slot. And this cartridge will play anything ever released during the 2600's lifespan (with one exception, see below) and most homebrews and reproductions (provided you can find a good dump of the ROM).
The Harmony Cart can be navigated with a joystick, paddle or driving controller. This is slightly annoying for the few games that principally use the Keyboard or Kid's Controllers because you will have to plug in a joystick to select the game and then replace it with the Keyboard or Kid's Controller.
BIOS updates used to be accomplished with a miniUSB cable and software available for Windows, Mac and Linux. The software will load an updated BIOS, downloaded from AtariAge, to the cart. The BIOS, v1.5, was last officially updated in 2010. However, as of v1.5, the USB method is no longer required, you can update the BIOS just by selecting it in the menu. There is a v1.6 beta BIOS available.
At least 80% of all Atari 2600 games ever made were released in 2KB or 4KB cartridges with nothing special inside them. Many later games use extra hardware to add bankswitching to get around the 4KB cartridge ROM limitation and memory to the paltry 128 bytes inside the 2600. Anything known to require no more than 32KB of ROM is supported. Here is a list of the bankswitching schemes each cartridge supports :
|CV (2K ROM + 1KB RAM)||CV (2K ROM + 1KB RAM)||CV (2K ROM + 1KB RAM)|
|F8 (8KB)||F8 (8KB)||F8 (8KB)|
|F8S (8KB with 128B SARA Super Chip RAM)||F8S (8KB with 128B SARA Super Chip RAM)||F8S (8KB with 128B SARA Super Chip RAM)|
|F6 (16KB)||F6 (16KB)||F6 (16KB)|
|F6S (16KB with 128B SARA Super Chip RAM)||F6S (16KB with 128B SARA Super Chip RAM)||F6S (16KB with 128B SARA Super Chip RAM)|
|F4 (32KB)||F4 (32KB)||F4 (32KB)|
|F4S (32KB with 128B SARA Super Chip RAM)||F4S (32KB with 128B SARA Super Chip RAM)||F4S (32KB with 128B SARA Super Chip RAM)|
|FA (12KB with 256B RAM+ RAM)||FA (12KB with 256B RAM+ RAM)||FA (12KB with 256B RAM+ RAM)|
|E0 (8KB)||E0 (8KB)|
|E7 (up to 16KB of ROM with or without 2KB of RAM)||E7 (up to 16KB of ROM with or without 2KB of RAM)|
|3F (up to 64KB)||3F (up to 512KB ROM and 32KB RAM)||3F (up to 32KB ROM and 4KB RAM)|
|F0 (Megaboy 64KB)|
|Starpath Supercharger (direct load from audio file)||AR Starpath Supercharger (binary conversion)|
|UA (8KB)||UA (8KB)|
|DPC (Pitfall 2)|
|Custom (DPC+, Star Castle, Chetiry)|
One important original game that the Harmony cart supports it Pitfall 2, which used a complex bankswitching chip that allowed for more complex sound and was not emulated in the earlier flash carts. For this and the sheer number of bankswitching schemes supported, and the ease of putting games on the cart and the number of games you can have on the cartridge, the Harmony cart has essentially made the older carts obsolete. The Harmony's firmware can be reprogrammed to support new bankswitching schemes.
In 2014, the maker of Harmony Cartridge, batari, released an updated model of the cartridge known as the Harmony Encore. The Encore can support games with a chip that can be configured as 512KB of ROM, RAM or any power of two combination. It costs $25 more, but the number of additional games it can play is severely limited at the moment. It adds support for the F0 Megaboy 64KB cartridge, the only cartridge released during the 2600's lifespan that reached 64KB in size.
It can play Boulderdash (3E, demos only, full game ROM not released) and Stella's Stocking (X07, ROM not released) and Zippy the Porcupine (demo only, full game ROM not released) homebrews. It also supports new bankswitching schemes, EF (64KB), DF (128KB) and BF (256KB), all with or without a 128B SARA chip. However, in my opinion there is precious little software for it to be worth the extra $$. In a year or two, my opinion may change. Moreover, you can upgrade your Harmony to a Harmony Encore for $25 by sending it back.