Atari 7800 System (American system with joystick controller)

Atari only had the 5200 console on the market for 2 years before pulling the plug. Management was unhappy that it only sold 1 million units after the original 2600 sold over 30 million units. The new 7800 console replaced the flourdering 5200 in the hope that market acceptance would be better.

Atari has been facing pressure from Coleco and its ColecoVision console, which supported graphics that more closely mirrored arcade games of the time than either the Atari 2600 or 5200. The Atari 5200 (released as a successor to the Atari 2600) was criticized for not being able to play 2600 games without an adapter.

  • MOS6502 CPU 1.79 MHz
  • 4KB RAM (2x 6116 2Kx8 RAM ICs)
  • 4KB BIOS ROM, 48KB allocated for the cartridge
  • Custom Graphics
    • 320×240 or 160×240
    • 256 colors (16 hues and 16 luma)
    • DMA support
    • 100 sprites maximum
  • MOS6502 RIOT
    • 2 joystick ports
    • cartridge port
    • expansion connector
    • power in

Graphics are generated by the custom MARIA chip, which uses an approach common in contemporary arcade system boards. It and is different from other second and third generation consoles. Instead of a limited number of hardware sprites, MARIA treats everything as a sprite described in a series of display lists. Each display list contains pointers to graphics data and color and positioning information.

MARIA supports a palette of 256 colors and 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 graphics found in the Nintendo Entertainment System and Master System, the processing demands of MARIA result in most games using the 160 pixel mode.

Each sprite can have from 1 to 12 colors, with 3 colors plus transparency being the most common. In this format, the sprite references one of 8 palettes, where each palette holds 3 colors. The background–visible when not covered by other objects–can also be assigned a color. In total, 25 colors can appear on a scan line.

The controller is redesigned from the earlier 2600 console. Had Atari used the same controller as the older console, they might have found more buyers. The move to 48KB for the cartridge was long overdue. ROM chips are inexpensive so 2 or 4 can be placed in a cartridge as needed.

Atari introduced a digital signature to prevent unwanted adult oriented games from being used. If a signature is not located, the 7800 remains in 2600 mode and MARIA is unavailable. All 7800 games released in North America had to be digitally signed by Atari. This digital signature code is not present in PAL 7800s, which use various heuristics to detect 2600 cartridges, due to export restrictions.