For a few years in the late 1980s, a Japanese Famicom owner who had finished a game could take the disk back to a toy shop, feed it into a kiosk and walk away with a different game on it for 500 yen. That was the promise of the Famicom Disk System, the add-on Nintendo launched on 21 February 1986. Its disks held more than the cartridges of the day, cost less to make, and could be written to, so a game could save a player’s progress without a battery.
Nintendo said that from then on the best Famicom games would be exclusive to the Disk System, and at first they were. The Legend of Zelda went on sale the same day, and Metroid, Kid Icarus and the first Castlevania all began life on disk. Retro Gamer reports that half a million units sold in the first three months and about 4.5 million in all. But the format never left Japan, and by the end of the decade publishers were going back to cartridges.
Fast facts
- Maker: Nintendo, for the Japanese Family Computer (Famicom), the console sold in the West as the Nintendo Entertainment System.
- Launched: 21 February 1986 in Japan, at ¥15,000.
- Parts: a disk drive (HVC-022) and a RAM adapter (HVC-023) that plugs into the Famicom’s cartridge slot.
- Memory: 32 KB of program RAM, 8 KB of graphics RAM and an 8 KB BIOS ROM, all in the RAM adapter.
- Media: the Disk Card, a modified Mitsumi Quick Disk, holding about 64 KB per side.
- Sound: one extra wavetable channel with frequency modulation, mixed with the Famicom’s own sound.
- Disk Writer service: ¥500 to rewrite a disk with another game, until 30 September 2003.
- Sales: about 4.5 million, all in Japan, according to Retro Gamer.
Why a disk
Cartridges were expensive. A game on a cartridge carried its program in mask ROM, made in a factory months ahead and in quantity. Edge summed up the Disk System in 1998 as “an attempt to counter rising ROM costs”, noting that disk games cost roughly half the price of cartridges. Retro Gamer gives the prices: Disk System games sold for about ¥2,500 to ¥3,000 when new cartridge games cost ¥5,000 to ¥7,000.
The disks also held more. Nintendo’s own description says a Disk Card had about three times the capacity of a ROM cartridge. When the Disk System was being prepared, Shigeru Miyamoto’s team treated Super Mario Bros., a 40 KB cartridge, as a last big cartridge game before the disks arrived. And a disk could be written to. Few cartridges of 1986 had battery-backed memory for saving, so an adventure that took several sittings needed a password or a disk. Retro Gamer quotes the collector Sean Corse: Metroid and Zelda “were long adventures that required multiple gaming sessions to complete, facilitated by the Disk System’s save feature”.
Two boxes and a cable
The Disk System came in two parts. The drive sat beside the console, powered by six AA batteries or its own mains adapter, and connected by a cable to the RAM adapter, a cartridge-shaped unit that plugged into the Famicom.
The RAM adapter did the real work. It held the memory the games loaded into and a custom chip, the RP2C33, which drove the disk interface, generated the extra sound, and provided a timer interrupt the Famicom itself lacks. The NESdev Wiki gives the memory map:
| Address | Contents |
|---|---|
CPU $6000-$DFFF |
32 KB of RAM, loaded from disk |
CPU $E000-$FFFF |
8 KB BIOS ROM |
PPU $0000-$1FFF |
8 KB of RAM for tile graphics |
Everything in that map is fixed; nothing is switched as it is on cartridge mappers such as the MMC1 or MMC3. A game loaded what it needed from disk into RAM, and loaded more when it needed something else. The BIOS ran at power-on, played the start-up screen, and offered routines for reading and writing files. The timer counts down once per CPU cycle and can raise an interrupt when it reaches zero, repeatedly if a game asks it to.
Sharp also sold the Twin Famicom, a console with the Famicom and the Disk System built into one case.
The Disk Card
Nintendo based its disk on the Quick Disk, a cheap format made by Mitsumi. A Quick Disk drive has only one motor. It stores data on a single spiral track, and the head moves in towards the centre as the disk turns, so there is no random access: a program waits for the head to reach the file it wants, much as it would on tape, only far faster. NESdev puts a full pass over one side at about seven seconds. The drive clicks as the head springs back to the start.
The commonly used disk image format holds 65,500 bytes per side, and the physical disk holds a little more. A double-sided card therefore carried about a megabit, which is how the team making Super Mario Bros. thought of it.
Nintendo built its own protections into the card. The case has recesses spelling “NINTENDO” that fit moulds inside the drive, so an ordinary Quick Disk will not go in. Each disk side begins with the text *NINTENDO-HVC*, and the BIOS refuses to read a disk without it. By convention, the first file on a disk was the licence screen shown at start-up, a file named KYODAKU- (Japanese for “permission”), and the BIOS checked for it before running the game.
The cards had tabs that could be broken off to protect a side from being written, like a floppy disk. What they lacked was a shutter over the magnetic surface. Retro Gamer’s contributor Laurent Kermel recalls that most disks relied on a wax-paper sleeve instead, so dust, fingerprints and scratches reached the film, and a disk left near a television’s speaker could be damaged by its magnets.
The extra voice
The RP2C33 adds one sound channel to the Famicom’s five. It plays a 64-step waveform that the program writes into the chip, so a game can shape the sound of the note, and a second unit bends the channel’s pitch in a pattern of its own. NESdev describes it as similar to the Game Boy’s wave channel “but with more sophisticated modulation”. Retro Gamer calls it an “additional audio channel for FM synthesis”, and the modulation does give it a family resemblance to FM. The musical shooting game Otocky used it to imitate different instruments.
Retro Gamer’s collector Corbie Dillard describes it as generally used for percussion-type effects in the background, and sometimes for extra sound effects. The Famicom’s cartridge slot has audio pins, which is how the RAM adapter’s sound reached the television; the NES’s slot has no such input (see the APU entry). When Zelda and Metroid were converted to NES cartridges, their music was altered to play on the console’s own channels; Dillard counts hearing the disk soundtracks among the reasons to collect the format.
The Disk Writer
The most unusual part of the system stood in the shops. Nintendo placed Disk Writer kiosks in retailers across Japan. Retro Gamer describes the arrangement: a blank Disk Card cost ¥2,000, and the kiosk would write a game onto it for another ¥500. A player could bring the same disk back and have a new game written over the old one. Nintendo’s own page gives the same ¥500 fee, with some exceptions. Edge in 1998 put it in sterling: games for “as little as ¥500 (£2.50)”.
A rewritten disk came without a box or a full manual. Miyamoto has explained that this is why Zelda ends its opening with “Please look up the manual for details”: Nintendo made the booklet worth having, with hints and story, so that players who rewrote a disk still had something to show for their purchase (the Zelda entry has the full account).
From 1987, Retro Gamer reports, Nintendo also ran score contests through Disk Fax machines in shops. Specially made blue disks of games such as Golf Japan Course recorded a player’s score, which the machine sent to Nintendo, and the best players won prizes.
Nintendo ended the disk rewriting service on 30 September 2003.
The games
The Disk System’s first year gave Nintendo several of its longest-running series.
- The Legend of Zelda, 21 February 1986, the same day as the hardware. Players saved their progress to the disk.
- Metroid, 6 August 1986, from Gunpei Yokoi’s R&D1. It also saved to disk.
- Akumajō Dracula, Konami’s first Castlevania, September 1986.
- Kid Icarus, December 1986, also from R&D1. Its team kept working until three days before release, because the finished master could be copied onto disks so quickly.
- Zelda II: The Adventure of Link, January 1987.
- Famicom Detective Club (1988) and its sequel (1989), the text adventures that Yoshio Sakamoto wrote for the format.
When these games came to the West, they came on cartridge. Zelda went into a gold cartridge with a battery to keep its save; Metroid and Kid Icarus gave the player passwords instead (see password systems and battery backup).
Why it faded
The Disk System’s advantages lasted only a few years. Retro Gamer quotes Kermel: “Soon after the release of the Disk System, cartridges reached the 128k mark and started to include inbuilt batteries.” Sean Corse makes the same point: the cost of cartridge ROM and of battery-backed saves fell until neither was the problem it had been in the early 1980s. With bank switching, a 128 KB cartridge already held more than both sides of a disk. The cartridge version of Zelda in 1987 showed that a disk was no longer needed for either.
Piracy hurt it too. A disk that a shop could rewrite could also be copied at home. Retro Gamer describes bootleggers linking two drives, programs that copied disks on a single machine, and Nintendo revising the drive and adding copy protection, which was cracked within months.
Publishers had their own reasons to leave. Retro Gamer reports that Nintendo asked for half the copyright in each disk game published by an outside company, and that the ¥500 rewrites left little room for profit. Edge listed “consumer confusion regarding a dual-format console, piracy and contractual problems with licensees” among the reasons disks were phased out.
The hardware aged badly as well. The drive turns the disk with a rubber belt, and the belts perish; Retro Gamer notes that many surviving drives need a new belt before they will read a disk, and Corse describes a cryptic disk error screen that shows only a number.
Retro Gamer reports that by 1989 many publishers had abandoned the format, and that shops complained that the unused kiosks were taking up space. Nintendo kept the rewriting service running until 2003. Edge, writing in 1998 as Nintendo prepared another disk add-on, the Nintendo 64DD, described the Disk System as having “fell far short of being the success it was intended to be”.
Sources
- Nintendo, Family Computer Disk System hardware page (Japanese, web): release on 21 February 1986; about three times the capacity of ROM cartridges; the save feature; the Disk Writer and its ¥500 fee, with some exceptions; the end of the rewriting service on 30 September 2003; six AA batteries or an AC adapter; the RAM adapter HVC-023. https://www.nintendo.com/jp/famicom/hardware/disksystem.html
- Retro Gamer: Videogames Hardware Handbook volume 2, 2010, “Retroinspection: Famicom Disk System”, pp. 220-225: the ¥15,000 launch price; half a million in three months and 4.5 million in all; disk game prices of ¥2,500-3,000 against ¥5,000-7,000 for cartridges; the Quick Disk basis; the “additional audio channel for FM synthesis”; Sean Corse on Metroid and Zelda; the ¥2,000 blank disk and ¥500 kiosk; Disk Fax contests from 1987 and the blue disks; the Twin Famicom; the missing shutter, wax sleeve and demagnetisation; piracy, copiers and revised drives; the half-copyright demand; Laurent Kermel on 128k cartridges with batteries; Corbie Dillard on the sound channel and the altered cartridge soundtracks; Corse on falling cartridge costs; the claim that the best games would be Disk System exclusives; the numbered disk error and drive belts; publishers leaving by 1989.
- Retro Gamer: Videogames Hardware Handbook volume 1, 2009, “The Family Computer” (John Szczepaniak): the February 1986 launch; blank disks at 2,000 yen and 500-yen rewrites; pirated copies; drive belts; Sharp’s combined machines.
- Edge issue 54, January 1998, 64DD feature: the February 1986 launch; “an attempt to counter rising ROM costs”; disks at roughly half the price of cartridge games; rewrites for “as little as ¥500 (£2.50)”; Zelda and Metroid first on disk; “consumer confusion regarding a dual-format console, piracy and contractual problems with licensees”; “fell far short of being the success it was intended to be”.
- Retro Gamer Collection volume 4, 2010, Castlevania history: Akumajō Dracula on the Disk System in September 1986.
- NESdev Wiki, “Family Computer Disk System” (community reference, web, secondary): the drive and RAM adapter part numbers; the RP2C33’s functions; the memory map; the Quick Disk mechanism, spiral track and seven-second pass; the “NINTENDO” recesses and drive protections; the timer IRQ. https://www.nesdev.org/wiki/Family_Computer_Disk_System
- NESdev Wiki, “FDS disk format” and “FDS BIOS” (community reference, web, secondary): 65,500 bytes per side in the common image format; the
*NINTENDO-HVC*check; theKYODAKU-licence file. https://www.nesdev.org/wiki/FDS_disk_format - NESdev Wiki, “FDS audio” (community reference, web, secondary): the 64-step wavetable, the modulation unit, the comparison with the Game Boy and Otocky. https://www.nesdev.org/wiki/FDS_audio
- Release dates for The Legend of Zelda, Metroid, Kid Icarus, Zelda II, Super Mario Bros. and the Famicom Detective Club games, and Miyamoto on the manual, follow the sources given in those games’ and people’s own entries.