Hi,
Recently I've been playing some WhompEm and wondeered what would happened if I could beat the bosses with the very weapons I get from them. I figured it couldn't be too hard to hack it in, just find a memory location where the weapons are stored.
I had no prior experience to NES development. I did play a bit with UZebox in the past, and have a basic knowledge of ASM and the NES architecture, but nothing vast. So I first tried with Nintendulator and couldn't find a tool for memory inspection, but found one in FCEUX. After a bit of fiddling I found a way.
I have to say that debugging retail NES games is a _lot_ of fun, and 6502 instruction set is really simple. I'm thinking about my next game to challenge. I've already played with Felix The Cat and almost made it so I can have all the weapons ingame regardless of the level type.
Anyway, I've written an article about basics of NES memory inspection and 6502 disassebly on my blog: http://retro-hack.blogspot.com/2015/04/ ... games.html
It's nothing special, and might have some technical errors (please point them out if you read it) but I figured it might make a nice read or even help another newbie a bit. I didn't go into too many details as I was pretty tired by the end. But I think it's not a waste of time, even though I haven't discovered anything new.
Recently I've been playing some WhompEm and wondeered what would happened if I could beat the bosses with the very weapons I get from them. I figured it couldn't be too hard to hack it in, just find a memory location where the weapons are stored.
I had no prior experience to NES development. I did play a bit with UZebox in the past, and have a basic knowledge of ASM and the NES architecture, but nothing vast. So I first tried with Nintendulator and couldn't find a tool for memory inspection, but found one in FCEUX. After a bit of fiddling I found a way.
I have to say that debugging retail NES games is a _lot_ of fun, and 6502 instruction set is really simple. I'm thinking about my next game to challenge. I've already played with Felix The Cat and almost made it so I can have all the weapons ingame regardless of the level type.
Anyway, I've written an article about basics of NES memory inspection and 6502 disassebly on my blog: http://retro-hack.blogspot.com/2015/04/ ... games.html
It's nothing special, and might have some technical errors (please point them out if you read it) but I figured it might make a nice read or even help another newbie a bit. I didn't go into too many details as I was pretty tired by the end. But I think it's not a waste of time, even though I haven't discovered anything new.