|Tehkan Gridiron Fight|
|CPU||3× Zilog Z80 @ 4.608 MHz|
|Sound||2× AY-3-8910 @ 1.536 MHz,
Oki MSM5205 @ 384 kHz
|Display||Color raster, horizontal orientation,
768 out of 4096 colors
Overview and control system
Tehkan Gridiron Fight is a two-dimensional top-down scrolling American football game in which the player(s) control the virtual player on their team who is closest to the ball, with the trackball determining the speed and direction at which the player runs. A single push-button labeled "Kick" causes the virtual player in possession to release the ball with the same force and direction in which he is currently running. (This button is duplicated on either side of the trackball for left or right-handed players.) The Player 1 (red trackball) side contained two additional push-buttons for choosing between Single or Two-Player games. Before each play, players are invited to select from a variety of formations, e.g. "Sweep" or "Draw". The formation selected is displayed on a seven-segment LED on the player's control panel.
Use of the third dimension
Although the graphics are two-dimensional, the height of the ball can be determined by its growing larger while its shadow appears on the ground. Also on the side of the screen is the score and a clock which counts down to zero, the point where the current game ends.
Two slightly different cabinet shapes were released - one with straighter edges and vertices in profile and one with more rounded edges akin to its stablemate, Tehkan World Cup.
Processors and sound
Tehkan Gridiron Fight used two Z80C 8-bit CPUs at 4.608 MHz for processing. For sound, it employed one Z80C at 4.6 MHz, two AY-3-8910s at 1.536 MHz and one M5205 at 384 kHz for FM and samples. Although this produced three-channel music plus sound effects, all sound was fed through a mono amplifier in the cabinet housing. As machines aged the amplifier was known to fail, resulting in silent gameplay.
Screen and resolution
The screen was a horizontally mounted 20" color raster CRT monitor fed at 256 x 224 pixels by 768 colors by 60 Hertz.
The game unit consisted of two 3" optical trackballs. These were made of semi-transparent plastic, illuminated from below such that they shined fairly brightly blue or red, depending on the color of the ball.
Relationship to Tehkan World Cup
Tehkan World Cup was a soccer video game released in the same year as Tehkan Gridiron Fight featuring almost identical hardware. It employed the same twin trackballs with an action button duplicated on either side and a similar cocktail cabinet design with horizontal screen. The primary hardware difference was the absence of the seven segment LED adjacent to the action buttons. The software of the two games exhibited a similar top-down two-dimensional window-on-the-field graphical design.