Pokémon Crystal and Action Replay

Pokémon Crystal and Action Replay
by socram8888 on 2011-05-20 (#78361)

I'm curious about why this Pokémon Crystal freezes when leaving a town, entering a house or something like that (reloading maps or GFX data, dunno) with the Action Replay Xtreme attached and enabled until you disable it with the switch, even with no cheat enabled.
The snapshot function and the game trainer still works. I thought the AR was designed to work transparently to the game running on the GameBoy

Also, anyone knows how does this device works? Using NMIs or something?

And a proposal: what about using the AR or GG to run code from a Gameboy Camera Save-RAM? There is 128kB of RAM, and data could be transferred using a GB<->PC transfer cable and "Receive photo"

by MottZilla on 2011-05-20 (#78373)

The AR usually has a "Master Code" right? This modification itself can cause the game to crash when AR is enabled I imagine. AR I believe hijacks the NMI interrupt or another to do its patching. It is the only way it can rewrite system memory as it's not like it has any direct connection to it.

by socram8888 on 2011-05-20 (#78374)

There are Master Codes for other RAM-only based systems (eg.: the DS), that indicates the AR where to put its bootloader. AFAIK the GBC AR doesn't require anyone for any game, because it simply disables the ROM (or SRAM?) from the game and puts there its own BIOS

Oh, forgot something: it works well with Pokémon Gold and Silver with no Master Code

EDIT: I've been searching with the bgb for reads on the 0000-0103 to see if the game checks the vectors but I haven't found anything useful

There is one of these checks just after boot and before the initial "NINTENDO / GAME FREAK / CREATURES INC" screen. The screen remains black (so the pallettes have been already loaded) until you turn the AR off

PS: Gameshark = Action Replay