Dungeons And Dragons Board Game From The 1980s Holds A TMS1100
Today is a little tour back to the early 1980s when Mattel released the DUNGEONS & DRAGONS Computer Labyrinth Game. [Cameron Kaiser] was dealing with a few boxes of old stuff when he came across the game. Lucky for us, he decided to do a full teardown and a comprehensive review more than 40 years after it came out.
The game itself is quite simple. You and a friend are characters on the board and navigate an eight-by-eight maze. As you move through the labyrinth, a microcontroller emits twelve audio cues that tell you what you’ve encountered (walls, doors, treasures, and so on). The eight buttons on the side allow you to hear the different sounds to know what they mean, as we imagine even the most well-written manual would struggle to describe them. In addition, the pieces are cast metal, which allows the game to track where the pieces are placed.
With great difficulty, [Cameron] opened the game to reveal a membrane keyboard pad to locate the various pieces. The actual PCB is relatively small, containing only a single 2N2222 transistor, a few resistors and capacitors, and one 28-pin Texas Instruments DIP. While the markings on the chip say M34012, this is a modified TMS1100, a descendant of the first microcontroller. It is a PMOS part, which allows it to run directly from a 9-volt battery with little or no regulation. Mattel needed something cheap and customizable to mass produce, and TI had just the design. You can give them a ROM, an instruction decoder PLA and an output PLA and get back a cheap little chip that you can get a million off of. [Cameron] has an annotated the shot based on an early TI patent and a TMS1000 the of [Sean Riddle].
The chip has only four inputs and nineteen outputs. This makes the keyboard difficult to scan, but the designers worked around it by using all the inputs and all but one of the outputs to read the keyboard. The architecture of the TMS1000 is a bit odd, with only a six-bit program counter. It breaks the ROM into 16 pages and has a 4-bit address register. However, the TMS1100 has double the ROM, so it has a one-bit head latch for the second bank. It was no power source, and came in one instruction per clock at a paltry ~475kHz (about as it tended to drift). Overall, it’s amazing how it does so much with so little.
It’s a beautiful read that takes you back to how they designed things back then. Despite all our progress over the years, we’d love to see more inventive, tactile games that use microcontrollers. So while it may not be Holo Chess, this microcontroller-powered game still adds some new ideas even after all this time.