Sega Game Gear
Portable Master System
Sega's 1990 colour handheld that was essentially a portable Master System, offering backlit graphics but suffering from poor battery life that limited its success against Game Boy.
The Sega Game Gear was Sega’s 1990 handheld that offered backlit colour graphics in a market dominated by Game Boy’s monochrome display. Essentially a portable Master System, it featured impressive specs but suffered from battery life issues that limited its commercial success.
Fast facts
- Released: 1990
- CPU: Z80 @ 3.58 MHz
- Screen: 160×144, 32 colours from 4096
- Battery life: 3-5 hours (6 AA)
- Price: $149
A Master System whose extra mode is switched on by the cartridge
The Game Gear is usually described as a portable Master System. The hardware documentation is more specific than that, and stranger:
The Game Gear VDP is identical to an SMS2 VDP except that: It does not initialise the palette for TMS9918a modes. It includes an additional Game Gear mode (enabled by the cartridge hardware) where: the palette depth is increased from 6 to 12 bits per pixel; the displayed screen area is reduced to just the central 160×144 pixel section.
Two things follow. The colour improvement over the Master System is real and large — 12 bits per pixel against six, so 4,096 possible colours rather than 64. And the distinguishing mode is turned on by the cartridge, not by software: whether the machine is a Game Gear or a Master System in a smaller case is decided by what is plugged into it.
The cropping is a window onto a full-size screen rather than a smaller screen, and the seams show:
- the top two rows are off-screen, so horizontal scroll lock “is not visible”
- the leftmost column is off-screen, so masking it achieves nothing
- and, most awkwardly, “the sprite limit can still occur for off-screen sprites”
That last is the eight-sprites-per-line limit inherited from the Master System, being consumed by sprites the player cannot see. A Game Gear programmer has to keep sprites off the parts of the screen that were never going to be displayed.
How a 256-pixel screen fits a 160-pixel panel
The LCD is a Citizen UC-320: 3.2 inches, super-twisted nematic, cold-cathode fluorescent backlight, and 160 × 146 dots — two rows more than the 144 the VDP crops to.
Playing a Master System game means fitting 256 pixels across into 160, and the method is remarkable:
256 pixels wide is reduced to 160 pixels by removing the first 8 and last 8 columns to make the width 240 pixels, then mapping three source pixels to two pixels of the display using sub-pixel mapping.
[RGB]1 [RGB]2 [RGB]3 = [RG1B2] [R2GB3]
Three source pixels become two displayed ones by redistributing their red, green and blue components across the panel’s own subpixels. It is the same trick modern font rendering uses for horizontal resolution, arriving on a 1990 handheld as a way to make somebody else’s console fit.
Vertically the machine simply drops rows — “not incrementing the Y value at every third row” — and the two Master System heights land differently. A 192-line game is padded with 13 rows of border above and below to reach 218, then scaled to 146, “this results in a letterboxed image”. A 224-line game has three rows removed top and bottom to reach the same 218 and comes out full screen. The 240-line mode is not supported at all.
So the taller Master System video mode, the one that “does not work properly on Mega Drives”, is the one that fills a Game Gear screen.
Stereo that the speaker ignores
Port $06 assigns each of the four PSG channels to the left or right side, one
bit per channel per side. It comes with a warning that shapes how Game Gear music
is written:
Note however that this only affects the headphone output. The built-in speaker is unaffected … If a channel is set to mute both sides, this has no effect on the speaker. Thus, don’t use this to mute the sound.
A channel silenced in both ears still plays out of the console. Panning is a headphone feature that the machine’s own speaker does not implement, so anything composed to use silence as an effect works on headphones and fails in the hand.
Specifications
| Component | Detail |
|---|---|
| Display | Backlit colour LCD |
| Resolution | 160×144 |
| Colours | 32 on-screen from 4096 |
| Sound | 3 pulse + 1 noise |
| Cartridge | Proprietary format |
Master System Compatibility
A special adapter allowed playing Master System cartridges:
- Near-complete library access
- Colour graphics on portable
- Existing game investment
Why It Lost to Game Boy
| Game Gear | Game Boy |
|---|---|
| 3-5 hour battery | 30+ hour battery |
| $149 price | $89 price |
| Large, heavy | Compact |
| Strong library | Tetris, Pokémon |
Notable games
| Game | Notes |
|---|---|
| Sonic the Hedgehog | Unique portable version |
| Columns | Pack-in puzzle game |
| Shinobi | Quality action |
| Various ports | Master System conversions |
Legacy
The Game Gear proved that technical superiority doesn’t guarantee success. Its battery consumption demonstrated that portable gaming requires different engineering priorities than home consoles.