Chris Covell released an bugfix for his Game Gear “HiColor” demo.

His notes:

Hi, folks. I’ve discovered (to my embarrassment) that this demo will not work properly on older GGs (without the BIOS) because I forgot to clear an important variable on startup. (The BIOS clears RAM beforehand, I’ll bet.) So, I’ve updated my demo and it should work fine on all Game Gear models.

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http://www.smspower.org/forums/viewtopic.php?t=6719