Gameboy ExChanger (GBX - GB Xchanger)

The (unofficial) GBX, produced by Bung Enterprises Ltd, was the best-known backup unit for Gameboy and Gameboy Color games. The device plugged into the parallel port of the PC and allowed dumping ROM and SRAM sumee data to PC, as well as rewriting flashcarts to play copies of Gameboy games.

The Gameboy Xchanger is a diddy little blue gadget that plugs into your PC and enables you to cram up to 250-odd of your existing GB games onto a single cartridge the same size as an ordinary one. It works with old mono games and the fancy new colour ones alike (you can mix and match the two types, although the colour ones are a lot bigger and you won’t get nearly as many of them on a cartridge at once), you can change the games over as many times as you want (writing a new cartridge is as easy as falling off a log and takes about a minute), and you get to select your games from an easy-to-use menu once they’re on there. The Xchanger even supports games which save your progress into the cart’s memory as you go along, like Zelda, and you can also use it to run free home-made games created by bedroom GB programmers, including brilliant versions of old Spectrum classics like Jet Set Willy and Jetpac.

The device is perfectly legal (although one of the reasons for its popularity is that it also lets you put commercial GB games downloaded from the Internet onto the cart, which entirely isn’t legal), and it’s even cheap, at just £25. (Blank cartridges come in various sizes, from £20 up to £60 for the biggest.) The GB Xchanger is a modern miracle of miniaturisation, and it’ll give your Game Boy or Gameboy Color a whole new lease of life.

GB XChanger - Legendary flash card kit made by Bung. It existed before the GBC but increased in popularity after the release of the GBC and the beginning of the GBC Scene. GB-XChanger with 64M Cartridge
These flash cards were available in 4Mbit, 16Mbit and 64Mbit sizes and had onboard SRAM for saving. Since virtually all GB/C games used SRAM for saving the kind of issues involved with GBA Saves were basically non-existant. Early V1 models had some problems with bank switching; this could be fixed with the help of a tool called "GBV1FIX". V1 and V2 cards can be distinguished by a large "V1" or "V2" printed on the circuit itself.

GBX-Tool v1.8 - latest software for GB XChanger

e-Merger by Netmars was the first GB/GBC Backup System that featured RTC support.

There were 16 MBit and 64 MBit versions of the e-Card available, both of them featured RTC support as well as a built-in Menu. Like most all the copiers at that time it connects to the PC via Parallel Port. It is possible to use it as a standalone unit, no PC is required to dump a Cartridge to e-Card and it can even be operated completely without power supply, getting power from a 9V Block battery. All necessary instructions to copy are given on a small 16*2 LCD.

Possible and not so provable ways the GBXemu name was born:
Update: GBoy explains - GBX - stands for GameBoy & GB Color and EMU is short for Emulation & Emulator and thus GBXemu

Grain Genes gbxR
Likelihood close to zero, but it is fun.

Pence Sterling GBX
but domains cost more so not likely.

DS Release Group GBX
but that one came well after the first one.

GBX emulator for PC
One of the working GB emulators for PC DOS. Closest name match, but the emu was totally unfinished and not so good. Well maybe.

GB XChanger (GBX)
This GB GBC rom backup tool was the most popular of the tools of this time and the timing looks about right... Spin-off sites
List of direct descendants as well as folks trying to make money off of the name.

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