Visualizing Commodore 64 memory in real-time... | Hacker News Reader

Visualizing Commodore 64 memory in real-time...

icu64.blogspot.com

30 pointsbprater5 comments

I started seriously hacking with my first Commodore 64, so this video brought me some really huge grins. Really gorgeous app for visualization.

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This is an awesome-looking tool. Similarly to other commenters, I had a DOS program when I was young called Game Wizard or something like that would compare memory states looking for values that changed or stayed the same, as some games tried to obscure their lives counter with addition and multiplication. Having the colored activity visualization would've made things even easier.

It would be cool to have something like this that works for modern native software, visualizing malloc()d/free()d blocks (or garbage collector behavior), etc., almost like a realtime Valgrind.

Very impressive!

I once had the ability to find infinite lives, and other cheats, in Commodore 64 games using just the Action Replay cartridge's machine code monitor. I'm not as hot at it as I used to be, though.

One important function is to be able to hop off up the CPU address stack to find more important functions higher up (so you're in a "Print a letter" subroutine, called by a "Print a word" subroutine). This isn't in ICU yet.

I spent a summer disassembling the code for Bolo on the Apple ][e, giving myself infinite lives or invulnerability, dissolving the maze edges and wandering around in general memory until I segfaulted the machine, disabling the enemy tanks by forbidding them from turning left - it was fantastic! I had printed the entire dump on green bar to do it.

Remember green bar?

I'll bet that printout is still at my Mom's in the attic somewhere.

I remember a program "ArtMoney" or some such from my early childhood. It would take snapshots of memory for a particular process, and allow you to search for a particular value. It supported a differential analyisis, such that you could enter the value of an easily controled variable (say HP), and then search for it, change the game state, search again, and narrow down the range of possible memory addresses.

Some previous discussion and a related blog post at http://news.ycombinator.com/item?id=793130

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