256 pixels

I’ve been restoring a Milton Bradley Microvision and am now happily at the point where I have a fully functional unit. Introduced in 1979, it’s known as the first portable game console with interchangeable cartridges. Anyone who has scoured eBay and yard sales for Game Boys knows that the monochrome LCDs of yore were fairly sensitive to heat and even just age. For a system ten years older than the Game Boy (and one that sold far fewer numbers), functional units are fairly hard to come by. But for a while, I’ve been invested in patching one together, and I plan to enjoy it until it, too, gives up the ghost1.

I’m not entirely sure why I’m so drawn to the Microvision, though I think a lot of it is the simplicity and purity that comes with a 1 bit 16x16 display. While this isn’t the system’s only limiting factor (the 16 bytes of RAM, 100kHz processor, and piezo buzzer are fine contributions), those 256 chunky pixels lend themselves to a very poetic design. Unfortunately, only 12 games were released (only 11 stateside), and as of yet I’ve only collected half of them, but the diversity shown proves that a lot can be done with a little. Part of the system design is that cartridges lay a mask over top of the display2 – this is an interesting way to play with the limited capabilities of the screen. Pinball adds four circular bumpers to the game screen, which the ball bounces off of; it also turns the upper corners into 45 degree angles which change the direction the ball bounces. Bowling has lines on the screen to denote ball return and gutters. Baseball’s overlay looks like a baseball diamond and shows where the fielders are3.

Internally, the unit is extremely simple. The processor is a Texas Instruments TMS110045, but it’s not a part of the console - every cartridge has its own processor. This was a cheap component at the time, and I can only imagine that the cost of the processor (with its internal ROM programmed for the game) was comparable to ROM and interface hardware. The TI chip was a commodity component, but the display driver (the only chip inside the console itself) was custom made by Hughes6 for the Microvision. The display itself was a custom component, and there wouldn’t have been an off-the-shelf solution for driving it. In light of this, it makes sense that the cost for the ‘special’ part would be placed on the unit, and an affordable chip bundled into each game (even if that did mean every cartridge having its own processor).

Externally, the system has a paddle (very 70s), and a 4x3 grid of rubbery buttons. The cartridge overlays this grid with either solid plastic (so you can’t press that spot), or a ‘button’ printed with what it does in-game (think Intellivision). These ‘buttons’ are cheap, crappy membranes on U.S. cartridges, and nice plastic buttons on European ones. The European buttons also use iconography or one-letter representations of what they do, presumably for localization purposes. It’s also worth noting that while all of the U.S. cartridges are kind of a beige-tan color, the European ones are bright, beautiful colors. They look better and the tactile buttons mean they play better, so they’re worth acquiring for the better games.

And what of the games? Well as mentioned, I only have a handful so far:

Eventually I’d like to complete the collection of carts (though Vegas Slots is pretty low priority), because it’s a neat system and it does a lot to show the potential of 256 pixels. There have been some modern hacker-type projects for minimalist systems, like the Meggy Jr. RGB, which uses an 8x8 RGB LED array. I wasn’t being disingenuous when I referred to these sorts of things as poetry earlier, I think it’s entirely apt. There’s a beautiful magic about working within a tight set of constraints, and figuring out how to extract something new from them. Microvision did this wonderfully, and it’s a shame the system didn’t catch on with third-party developers.

  1. Apparently someone is trying to get new LCDs manufactured for these. Fingers crossed. ↩︎
  2. Jay Smith, the designer, went on to design the Vectrex. The Vectrex, too, had a limited display (a monochrome vector CRT), and it, too, used overlays to make more of that situation. ↩︎
  3. The game is unable, of course, to factor in the shift, which kind of wrecks the realism as far as 2018 baseball is concerned. ↩︎
  4. The TMS1100 is a 4-bit processor with 54 instructions and inbuilt RAM, ALU, and oscillator. It’s well-documented; the programming guide is available here. ↩︎
  5. Apparently some actually used Intel 8021 processors (and required two 9v batteries), but MB apparently ported all of the Intel games over to the TI chip and made that the canonical processor. I’m not sure how many Intel versions of the system (wired for two batteries) or cartridges are out there. ↩︎
  6. These have date codes on them, my unit with the functional screen seemingly was from 1980. ↩︎