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Some NES titles were developed by companies who had licensed their title from a different arcade manufacturer. While the creator of the NES version would be restricted from making a competitive version of an NES game, the original arcade copyright holder was not precluded from licensing out rights for a home version of an arcade game to multiple systems. Through this loophole, Atari 7800 conversions of Mario Bros., Double Dragon, Commando, Rampage, Xenophobe, Ikari Warriors, and Kung-Fu Master were licensed and developed.
By June 1988, the Atari 7800 had sold more than 1 million units worldwide.
The Atari 7800 remained officially active in the United States between 1986 and 1991 and in Europe between 1989 and 1991. On January 1, 1992, Atari Corp. formally announced that production of the Atari 7800, the Atari 2600, the Atari 8-bit computer line, and the Atari XE Game System would cease. (It has since been discovered that Atari Corp. continued to develop games such as Toki for the Atari 7800 until all development was shut down in May 1993. By the time of the cancellation, Nintendo's NES dominated the North American market, controlling 80% while Atari Corp. controlled just 12%.
Despite trailing the Nintendo Entertainment System in terms of number of units sold, the 7800 was a profitable enterprise for Atari Corp., benefiting largely from Atari’s name and the system's 2600 compatibility. Profits were strong owing to low investment in game development and marketing.
Technical specifications Edit
- CPU: Atari SALLY 6502 ("6502C")
- Speed: 1.79 MHz, drops to 1.19 MHz when the TIA Television Interface Adaptor or RIOT (6532 RAM-I/O-Timer) chips are accessed
- (note: Unlike a standard 6502, SALLY can be halted to allow other devices to control the bus)
- RAM: 4 KB (2 6116 2Kx8 RAM ICs)
- ROM: built in 4 KB B
- Graphics clock: 7.15 MHz
- Line buffer: 200 bytes (double buffering), 160 sprite pixels per scanline, up to 30 sprites per scanline (without background), up to 100 sprites on screen
- Sprite/zone sizes: 4 to 160 width, height of 4, 8 or 16 pixels
- Colors per sprite: 1 to 12 (1 to 8 visible colors, 1 to 4 transparency bits)
- I/O: Joystick and console switch IO handled by 6532 RIOT and TIA
- Ports: 2 joystick ports, 1 cartridge port, 1 expansion connector, power in, RF output
- Sound: TIA video and sound chip, same as the 2600. Only the sound is used in 7800 games. Both video and sound are used in 2600 games.
- Optional POKEY sound chip on cartridge for improved sounds.
The graphics are generated by a custom graphics chip called MARIA, which uses an approach to graphics commonly used in arcade game system boards at the time. It was very different from other second and third generation consoles. Instead of a limited number of hardware sprites, MARIA allows for a much larger number of sprites described in a series of display lists. Each display list contains sprite entries with pointers to graphics data, color information, and horizontal positioning. The same display list is used for multiple rasters with the pointers being automatically adjusted. However, managing and displaying a large number of sprites required much more CPU time (both directly and indirectly since the MARIA would halt the CPU when drawing sprites) than consoles with hardware sprites and backgrounds.
MARIA has a number of different graphics modes which are either 160 pixels wide or 320 pixels wide. While the 320 pixel modes theoretically enable the 7800 to create games at higher resolution than the 256 pixel wide individual sprite can use from 1 to 12 colors, with 3 colors (plus a 4th "transparency" color) being the most common. In this format, the sprite is referenced to one of 8 palettes, where each palette holds 3 assignable colors. There is also an assignable background color, which will be visible wherever another object has not covered it up. In total the system can utilize 25 colors on a scanline at one time.
The graphics resolution, color palette assignments, and background color can be adjusted in between scanlines. This technique is documented in the original 1983 "Atari 3600 Software Guide". Games often used this feature to render high resolut
The Atari 7800 does not support backward compatibility for Atari 5200 games or accessories.