In the United States and Europe, if you wanted to save a game on your NES, you generally had two options. If the game supported password saves, you had to write down the password (accurately) and enter it back when you wanted to play the game again. Some games had rather lengthy passwords, and if you confused a 0 for a O or a 1 for an l, your password would be unusable. A relatively few NES games also had battery backup saves where the contents of a RAM chip inside the cartridge would be saved with a coin-style battery when the power was shut off. Early games required the problematic "hold reset as you turn the power off" method, and if the battery ran out replacing it was no easy task in the early days. Japanese Famicom players had a few more options, and as these can be rather obscure to westerners, I would like to talk about them here.
Family BASIC + Famicom Data Recorder
The Family BASIC package came with the Family BASIC cartridge and the Family BASIC Keyboard. The first release of BASIC cartridge was an ordinary cartridge without memory controller hardware but did implement 2KB of S-RAM for program storage. The second release of the BASIC cartridge, v3, contained 4KB of S-RAM for program storage.
What was interesting about the RAM inside the BASIC was that its contents were not retained after the console was turned off by a soldered-in coin-cell battery. Instead it used 2xAA batteries in a compartment inside the cartridge to save BASIC programs. There was a switch on the front of the cartridge to turn the memory protect function on or off. If the function was off, then the S-RAM would not be powered when the console was shut off.
However, 2K or even 4K was not enough to store long or many programs. The RAM on the cartridge was essentially a short-term storage solution, similar to the sleep mode found on GBA and DS cartridges. The Family BASIC Keyboard, in addition to the keyboard circuitry, contained circuitry to pass audio through to the Famicom Data Recorder. The Famicom Data Recorder is an ordinary cassette recorder that has the red and white styling of the Famicom. The cable that goes to the Mic port is used to write data to a cassette, the cable that goes from the Ear port is used to transmit data to the Famicom.
The Family BASIC Keyboard connects to the Famicom via the Expansion Port. Three other Nintendo games, Excitebike, Mach Rider and Wrecking Crew could use the Family BASIC Keyboard and the Famicom Data Recorder to save custom levels/tracks to tape and load them back after the console had shut off. Castle Excellent also supported this method, but you have to use Controller II to get to the save/load menu. Lode Runner and Arkanoid II also use this method, and the Arkanoid II paddle has a passthrough connector for the Keyboard. Nuts and Milk was rumored to support this method, but it does not.
The key to saving games is the Keyboard. Keyboards are not the cheapest things around. This circuit can do the trick for the NES : http://nesdev.com/tapedrv.PNG The ASCII Turbo Stick II also has the audio jacks and circuitry built in that required for this function. The Hori SD Station also has this functionality. Although the Hori Game Repeater also has audio in/out jacks, that may only be used for the device's function, which is to make a permanent record of button presses once the console is turned off.
Lode Runner refuses to show the Save/Load menu unless the Keyboard is plugged in, so these other methods may not work with that game. The U.S. version of Lode Runner retains the functionality, but connecting a keyboard to a NES was not likely to have occurred during its original lifespan. When Caste Excellent was released as Castlequest in the US, the Controller 2 menu was retained but the Save and Load commands were removed. However, you were given 50 lives instead of 5 to compensate for the loss of the ability to save your progress to tape. For Nintendo's own NES games, they kept the save/load function in the game, but they warned in the manuals that it was intended for future expansion. Nintendo could have implemented the Keyboard using the NES's Expansion Port, but they never released anything that used it.
Of these games, all but Castle Excellent only allowed you to save user-created levels to tape. Castle Excellent was the only game to allow you to save your in-game progress. In this sense, its saving is akin to the Famicom Disk System, which also used magnetic media to save game progress.
ASCII TurboFile & TurboFile II
The ASCII TurboFile is a pyramid-shaped box that plugged into the Famicom Expansion Port and provided 8KB of S-RAM to games that supported the peripheral. This S-RAM could store game information after the cartridge was turned off. The S-RAM was kept alive with 2xAA batteries. If you need to change batteries, it is best to do so while the device is connected to a Famicom that is powered on. If for some reason you cannot locate a Famicom, then you can probably save the data if you replace the batteries really quickly.
The Turbo File II had 32KB of RAM split into four banks. Each bank could be selected by a switch on the device. Both devices had a memory protect switch to protect against accidental overwriting.
Except for two games, the only games that supported this peripheral were games released by ASCII. Most of them will have a logo with "TF" on their labels. The Wizardry games present the most interesting use of the device. The Wizardry games have battery backed memory inside their cartridge. The first game, Proving Grounds of the Mad Overlord, allows you to transfer that memory to and from the Turbo File. Given that disaster can strike in Wizardry without mercy, this is a useful feature. I am unsure whether multiple games can save their data to an 8KB TurboFile.
The next game in the cartridge series, Legacy of Llylgamyn, could do the same thing as its predecessor but it could also allow you to import characters created in the first game. The final game, The Knight of Diamonds, allows you to import characters created in the first or second games in addition to backing up its internal memory. The NES releases of Proving Grounds of the Mad Overlord and The Knight of Diamonds had this feature removed.
The Japanese version of River City Ransom, Downtown Nekketsu Monogatari, was one of the three non-ASCII games that supported the Turbo File. You could use the Turbo File to save characters instead of the rather long passwords. US players only had passwords to allow them to restore their characters.
ASCII made a Turbo File Twin for the Super Famicom and as well as a Super Famicom adapter for the Turbo File II. The Turbo File Twin has legacy support for the Turbo File II, but the device's only plug is SNES-shaped. The closest device that western gamers enjoyed would probably be the Turbo Booster Plus for the TurboGrafx 16, which could save certain games to battery backed memory instead of requiring passwords.
This is the list of supported games from Wikipedia and NES Cart db, all published by ASCII unless otherwise noted :
Best Play Pro Yakyuu
Best Play Pro Yakyuu '90
Best Play Pro Yakyuu II
Best Play Pro Yakyuu Special
Derby Stallion - Zenkoku Ban
Downtown - Nekketsu Monogatari (Technos)
Dungeon Kid (Bothtec/Quest)
Haja no Fuuin
Itadaki Street - Watashi no Mise ni Yottette
Money Game II, The: Kabutochou no Kiseki (Sofel)
Wizardry - Legacy of Llylgamyn
Wizardry - Proving Grounds of the Mad Overlord
Wizardry - The Knight of Diamonds
One is whether Castle Excellent from ASCII really supports the Turbo File. Wikipedia claims support, and this site described how Castle Excellent saves differently to the TurboFile compared to later games : http://problemkaputt.de/fullsnes.htm However, this video could not make the game work with real hardware : https://www.youtube.com/watch?v=skkpzk3_vcU
I am not sure whether Haja no Fuuin really supports the TurboFile as well, but that may be due to the language barrier. Wizardry - Proving Grounds of the Mad Overlord and Fleet Commander have clearly labeled in-game options for the Turbo File even though they do not have the TF logo. Best Play Pro Yakyuu Special and Derby Stallion - Zenkoku Ban have the logo on their boxes but not their cartridge labels.
Bandai's Datach Joint ROM System and EEPROM Cartridges
EEPROM saving would become much better known with Sega Genesis cartridges and later N64 and GBA cartridges. EEPROM does not require a battery to keep its memory contents, can be programmed in bytes rather than blocks, and can be implemented cheaply. It is only good for games requiring low amounts of save memory.
Bandai loved gimmicky devices, and the Bandai Datach Joint ROM System was one of them. This device used a large base containing the CHR-RAM, the mapper chip and a barcode reader. Small cartridges would only include a PRG-ROM chip containing the whole game which would plug into a special cartridge slot on the Datach base unit. The Datach device contained a 256 byte EEPROM, but only one of the seven games used it for saving. One of the games, Battle Rush: Build Up Robot Tournament I believe, contained its own 128 byte EEPROM for saving instead of using the EEPROM inside the Datach unit.
Baindai used EEPROM in some of its standalone cartridge games. Four games used 128 byte 24C01 EEPROMs and six games used 256 byte 24C02 EEPROMs. No other company was known to have used EEPROMs in their Famicom games, but Konami had apparently intended its VRC2 chip to interface with an EEPROM. Konami's implementation was flawed, so it used the normal method of battery backed S-RAM for its games.