Turbo File

The Turbo File (for Family Computer) is a Famicom expansion port peripheral developed by ASCII Corporation, and is used to store save data for certain games. Variants of the device were also produced for the Game Boy (Turbo File GB), Game Boy Advance (Turbo File Advance), and Super Famicom (Turbo File Twin). Original Famicom Turbo File devices can be connected to a Super Famicom using an adapter unit, allowing certain SFC games to use the device in lieu of the TFTwin.

The device exists in two iterations; the original model (AS-TFO2) containing 8K of battery-backed SRAM, and the Turbo File II (AS-TF21) containing 32K of battery-backed SRAM (HM62256ALP-15). Both devices have an LED that illuminates when connected to a Famicom that is powered on, as well as a write protect switch to prevent accidentally overwriting save data. The TFII's 32K SRAM is split into four 8K banks that are manually switched, allowing for four individual saves.

Famicom games that support the Turbo File include:

• Best Keiba - Derby Stallion (1991)
• Best Play Pro Yakyuu II (1990)
• Best Play Pro Yakyuu Special (1992)
• Castle Excellent (1986)
• Derby Stallion - Zenkoku Ban (1992)
• Downtown - Nekketsu Monogatari (1989)
• Dungeon Kid (1990)
• Famicom Shougi - Ryuuousen (1991)
• Fleet Commander (1988)
• Haja no Fuuin (1987)
• Itadaki Street - Watashi no Mise ni Yottette (1990)
• The Money Game 2 - Kabutochou no Kiseki (1989)
• Ninjara Hoi! (1990)
• Wizardry - Legacy of Llylgamyn (1989)
• Wizardry - Proving Grounds of the Mad Overlord (1987)
• Wizardry - The Knight of Diamonds (1991)

Most titles bear a "TF" logo on the cartridge label signifying their compatibility.

Games that are believed to potentially work with the device (but remain unconfirmed) include:

• Castlequest (1989) (US version of Castle Excellent.)
• Kunio 8-in-1 (Pirate multicart that contains Downtown - Nekketsu Monogatari listed as "HEROS STORY" in the selection menu.)

Memory Setup and File Format

The first byte of memory (offset 0000h) is unused, potentially out of fear that certain games with controller access might disrupt it, so a dummy byte is used to skip it after resetting the address. All the rest of the space (0001h-1FFFh) is used to store save data, with files being attached directly after each other. Invalid file IDs indicate the start of free memory.

The majority of Turbo File games utilize this format for save files:

2   ID "AB" (41h,42h)
2   Filesize (16+N+2) (including title and checksum)
16  Title in ASCII (terminated by 00h or 01h)
N   Data Portion
2   Checksum (all N bytes in Data Portion added together)

The exception to this, Castle Excellent, uses a unique file format, shown here:

1   Don't care (should be 00h)    ;fixed, at offset 0001h
2   ID AAh,55h                    ;fixed, at offset 0002h..0003h
508 Data Portion (Data, end code "BEDEUTUN", followed by some unused bytes)

This game also forgoes a filename and utilizes a hardcoded memory offset of 511 bytes (0001h-01FFh). Due to the hardcoded memory offset, Castle Excellent will destroy any other file that is located at the same address. Some later games for both the Famicom and Super Famicom (including Fleet Commander) are able to properly manage the Castle Excellent save file.

Reference

• nocash's NES documentation: https://problemkaputt.de/everynes.htm#storageturbofile