Game Gear:Region Information
Unlike most other handhelds, not all Game Gears are the same throughout the world. In terms of software, there are two main regions for the Game Gear, Japanese and export, with the region being determined by a pin labeled JAP on the main ASIC (or the SCA on VA0 systems). If the pin is held high (connected to 5V), the system is set to export mode; if held low (connected to GND), it is set to Japanese. Most Game Gear games ignore this setting, though some such as Puyo Puyo and Streets of Rage will change depending on region. For example, if Puyo Puyo is played on an export system, the in-game language changes to English and the title screen also changes to the title "Puzlow Kids". Streets of Rage will become Bare Knuckle if played on a Japanese system. The region pin also affects Master System games, as some will display a Sega Mark III splash screen and have Japanese text if played on a Japanese Game Gear.
The only Game Gear game which has any sort of region locking is the Japanese exclusive Pop Breaker, which will not progress past the title screen on non-Japanese systems. However, this is actually the result of a programming bug rather than a deliberate attempt at region locking[1], especially since it was released several months before the Game Gear was released outside Japan.