The AY-3-8500 chip: closer view
GI's AY-3-8500 chip uses a simple
28-pin DIL package. Curiously, this chip has four pins that are not used. GI
could have used a smaller 24-pin package instead, but the use of a 28-pin
package could be due to some kind of ascendent compatibility: maybe some more
advanced versions could use the same package with the same pinout, and with
the four pins used for extra features. This has to be verified and it is still
unknown if some other similar chips used the same pinout.
Excepted the package, this chip has an interesting feature: the use of several video outputs. Rather than using a single video output pin, the chip has four outputs: one for each player, one for the ball, and one for the playing field (vertical line, scores, etc...). This gives the possibility of using a black and white video signal, as well as using one color for each output. Thus, it could be possible for example to draw the playing field in white with a green background, one player in blue and the other player in red. However, the electronic components allowing this were not cheap at this time, and due to the number of manufacturers of PONG systems, the price was a very important feature that could either result in a success, or a failure. This is why most of the systems equiped with the AY-3-8500 used black and white display, sometimes with grayscales (grey background, white playing field and scores, etc...). Talking about color PONG systems, we should not forget that the direct competitor, the MM-57105 from NS, allowed to output color pictures directly.
Finally, GI has released the AY-3-8510 chip, a derivate of the AY-3-8500. This chip uses a much smaller package (16 pins only) for three reasons: a single pin to select the games (instead of 6), a single pin for the video output (instead of 5) which is now in color, and 4 pins removed as the shooting games were also removed. This chip was released around 1978, and a very few systems use it (the only one known so far is the Coleco Telstar Colortron). Technically, it has one advantage and one drawback: if it does not allow playing the two shooting games, it offers a picture in color.
GI's AY-3-8500 chip
Pinout of the AY-3-8500
The AY-3-8510 game chip, much smaller.