The SEGA game gear was released in a time where official development kits were fairly rare and many third parties instead made their own using their existing Z80 knowledge and hardware. However a few official development kits have been found!
The Game Gear development board was most likely distributed to SEGA first party developers, but it is unclear if it was ever sold to third party developers.
It is incredibly rare and this is the only one that we know that exists so it is likely it was just a SEGA in house kit that wasn’t distributed to outside developers.
The image on the left is from the excellent Andrew Earley (@AndrewEarley7).
Find of the week! Sega Game Gear Development Board!! There’s a lot of mystery with this board because there’s little to no info if it online and the cartridge port is for Master System carts. I’ll be mailing this to @GerryRobotics to replace capacitors and get the unit working! pic.twitter.com/SsV8OXdCs6— Andrew (@AndrewEarley7) May 28, 2020
Although the original ebay link was never archived, it seems there was a ZAX ICE on sale that was used for Game Gear development 1.
Sega also distributed these for Sega Mega Drive development due to the sound chip being a Z80 processor.
Similar to the Nintendo Wide Boy, this was custom Game Gear hardware that could output to a standard Television.
This was distributed to magazines and other media producers so that they could get good screenshot from the hardware.
This would also have been used to create screenshots for Box Art and Manuals provided with the game. It may also have been used by developers and QA to make it easier to test the game on original hardware.
The hardware was featured in the American magazine Electronic Gaming Monthly (EGM) issue 27 2.
Some pretty sweet Sega GameGear development EEPROM carts shown in this article...Nice! 😎👌 https://t.co/mWmhQWM098 pic.twitter.com/Nw2vKvvHP6— BehindTheCode (@GerryRobotics) May 1, 2020
As official SEGA development kits were pretty expensive for the average game development studio, many third parties created their own custom Game gear development kits.
We have an entire page covering the Krisalis Development Kit which was used for both Game gear development along with Sega Master System development.
Krisalis Development Kit (Sega Master System/Game Gear)
For more information on the Krisalis Development Kit check out this post.
There is very little information on the internet about this development board or even who “Realtime” or “riverrun” were. If you have any more information please let us know!
There was a post about this board on SMS power and user TmEE believes it is a variant of the Romulator 4.
You can find more information about the Romulator in the SNES development section but this is unconfirmed and looks pretty different to the SNES Romulator.
Page 32 of Electronic Gaming Monthly (EGM) issue 27 ↩
View topic - Realtime / Riverrun development board for Game Gear & Super Ni**do - Forums - SMS Power! ↩