GB XChanger
From PHWiki
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. It belonged to the third incarnation of the MGD (Multi-Game Doctor) series of video-game copiers from this manufacturer.
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General Information
The associated Docotor GB 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. The XChanger linker, which connected to the printer LPT port, was used to flash these cards as well as to backup existing cards and backup and restore SRAM saves. After Nintendo filed a lawsuit against Bung in Hong Kong in 2000 the name of the MGD brand was changed into "Mr. Flash", with the GB XChanger becoming "Flash Linker" and the Doctor GB cards "Mr. Flash cards" (see also "Bung Enterprises Ltd." at Wikipedia).
Hardware
LPT Cable
The LPT cable needs two one-to-one connected male DB-25 connectors on each side ("straight through"). Laplink cables aren't compatible. The length of the cable shouldn't exceed 2m or 6ft.
Power
The GB XChanger worked with six 1,5V AAA Batteries or a DC Power supply, though powering it with a power supply was preffered, as this was far more reliable. Anything from 7-12V and 125mA-1A and center negative polarity should work, best results were achieved with 9V/500mA-1A ones, e.g. from a Sega Genesis, Master System or Game Gear PSU.
Software
GBX-Tool
MFM from Eurasia wrote an excellent flashing tool GBX-Tool for use with the XChanger.
DGBMax
DGBMax [1] was written by Emperor^DBZ's, it features a nice GBC menu with on-the-fly IPS patching and extended color support for old Gameboy games. Its flash function only works under the Windows 9x series of OSs. On XP it can still be used to create Multi-image ROMs which can then be flashed with the afore mentioned GBX-Tool.
Ucon64
Ucon64 [2] is an open-source CLI tool available for a wide variety of operating systems.
GBT
This is the obsolete official Bung flashing software for the GB XChanger.
Versions
There was one Hardware revision which affected the 16M Card and the linker, both versions can be distinguished by the Version number ("V1" and "V2") printed on the PCB. V1 Doctor GB card models had some problems with bank switching; see "Problems" section of this Article for further information. V2 linkers couldn't flash EMSs 16 MBit GB Transferer cards anymore. Even though there is a "V2" printed on the 64M cards PCB there always was only this version available.
Problems
Write Errors
The following errors with certain flash programms can be fixed with a tool called "cardfix":
GBX-Tool / by MFM
write_eeprom error! 0 or Error: Card Erase Failed!
GBT / by Bung
write cart error at bank=xx
Bank switching
this could be fixed with the help of a tool called "GBV1FIX" by Eurasia and Nightfall.
What IS the actualy bug? ------------------------ The old Bung cart has an extra register which seems to select whether the cart should run in 4mbit or 16mbit mode. This register is changed by writing to 6000-7FFF (the same way you select ROM bank). The only important bit in the register is bit 0. If it's set (1), which is default, the cart runs in 16mbit mode. If it's cleared (0), the cart runs in 4mbit mode. This means you can't access ROM bank 32-127! When reading from ROM bank 40, you actually read from ROM bank 8. Some games does some "clever" coding and writes to this area (in Asterix & Obelix, this happens after the end of a sound effect).
(From GBV1FIX readme)
Unknown reason
Several old Gameboy games have problems with V1 as well as V2 Cards, resulting from another problem, fixes for them are available at No Frills. In GoodGBX Sets these ROMs have the flag [BF].
