I have been working on reverse engineering the ROM of the NES game, Gauntlet II (I own a copy of 1 AND 2 btw), and as I was vigorously trying to manipulate level data, I noticed two very curious things that made me thing very hard. The game stores at least one whole copy of the map it is currently using in SRAM (~ $6000 - $63FF), and the rom data for levels is transferred into PPU memory, which starts at $1800 and goes off into wherever it goes (too lazy to check). So, this makes we want to ask: Is this pointing to the fact that SRAM can be used in some sort as RAM? Also, how in the world can parts of PPU memory be used as RAM / ROM space as well? I mean, I have analyzed disassemblies, and I have determined that PPU memory is used like this by strategic writes to 2006 and reads from 2007, but WHY use PPU memory? Is this because the part of level data in ROM is located in a 24 bit range? This is intriguing me, and I am curious if anyone has noticed this in other games, and if it is common. I also would like if anyone can answer my questions.
Final note: this game using the MMC3 mapper. Not sure if that has anything to do with the RAM usage.
Thanks for reading!
Final note: this game using the MMC3 mapper. Not sure if that has anything to do with the RAM usage.
Thanks for reading!