Gamegenie/Shark Cheats - Revision history

Nitro2k01 at 02:41, 5 April 2020

2020-04-05T02:41:40Z

Xzakox at 13:01, 28 June 2009

2009-06-28T13:01:35Z

Xzakox: New page: Game Shark and Gamegenie are external cartridge adapters that can be plugged between the gameboy and the actual game cartridge. Hexadecimal codes can be then entered for specific games, ty...

2009-06-28T11:07:00Z

New page: Game Shark and Gamegenie are external cartridge adapters that can be plugged between the gameboy and the actual game cartridge. Hexadecimal codes can be then entered for specific games, ty...

New page

Game Shark and Gamegenie are external cartridge adapters that can be plugged between the gameboy and the actual game cartridge. Hexadecimal codes can be then entered for specific games, typically providing things like Infinite Sex, 255 Cigarettes, or Starting directly in Wonderland Level PRO, etc.

===Gamegenie (ROM patches)===
Gamegenie codes consist of nine-digit hex numbers, formatted as ABC-DEF-GHI, the meaning of the separate digits is:

AB New data
FCDE Memory address, XORed by 0F000h
GI Old data, XORed by 0BAh and rotated left by two
H Don't know, maybe checksum and/or else

The address should be located in ROM area 0000h-7FFFh, the adapter permanently compares address/old data with address/data being read by the game, and replaces that data by new data if necessary. That method (more or less) prohibits unwanted patching of wrong memory banks. Eventually it is also possible to patch external RAM ?
Newer devices reportedly allow to specify only the first six digits (optionally). As far as I rememeber, around three or four codes can be used simultaneously.

===Game Shark (RAM patches)===
Game Shark codes consist of eight-digit hex numbers, formatted as ABCDEFGH, the meaning of the separate digits is:

AB External RAM bank number
CD New Data
GHEF Memory Address (internal or external RAM, A000-DFFF)

As far as I understand, patching is implement by hooking the original VBlank interrupt handler, and re-writing RAM values each frame. The downside is that this method steals some CPU time, also, it cannot be used to patch program code in ROM.
As far as I rememeber, somewhat 10-25 codes can be used simultaneously.

← Older revision		Revision as of 02:41, 5 April 2020
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−	{{Pandocs\|~~gamegeniesharkcheats~~}}	+	{{Pandocs\|game-genie-shark-cheats}}
	Game Shark and Gamegenie are external cartridge adapters that can be plugged between the gameboy and the actual game cartridge. Hexadecimal codes can be then entered for specific games, typically providing things like Infinite Sex, 255 Cigarettes, or Starting directly in Wonderland Level PRO, etc.		Game Shark and Gamegenie are external cartridge adapters that can be plugged between the gameboy and the actual game cartridge. Hexadecimal codes can be then entered for specific games, typically providing things like Infinite Sex, 255 Cigarettes, or Starting directly in Wonderland Level PRO, etc.

← Older revision		Revision as of 13:01, 28 June 2009
Line 1:		Line 1:
		+	{{Pandocs\|gamegeniesharkcheats}}
	Game Shark and Gamegenie are external cartridge adapters that can be plugged between the gameboy and the actual game cartridge. Hexadecimal codes can be then entered for specific games, typically providing things like Infinite Sex, 255 Cigarettes, or Starting directly in Wonderland Level PRO, etc.		Game Shark and Gamegenie are external cartridge adapters that can be plugged between the gameboy and the actual game cartridge. Hexadecimal codes can be then entered for specific games, typically providing things like Infinite Sex, 255 Cigarettes, or Starting directly in Wonderland Level PRO, etc.