Wanting to learn how to make a DK Rom Hack/Mod

[VGA Guy]

Okay, so apparently I've posted something to this effect before but I completely forgot about it.
I'm doing this again because I have some clearer ideas of what I want to do with it.

Ultimately I'd like to make some small edits to most of the main stages, as well as add two new ones that use mechanics already in the game in a different way. One focuses on wild barrels, and the other focuses on the springs, though I'd have to make them go all the way across the screen and have more than one. I'd imagine these would be feasible, but I haven't seen it done before.

I know this won't be easy, as each stage is kind of its own self contained program, but I do want to learn how to do this. Any advice, utilities, useful code, etc would be appreciated. I have minimal assembly knowledge, but I can figure it out a bit.

Thanks,

VGA Guy

[PaulGoes]

Hi VGA Guy,

I can give some pointers to get you started.

The most important resource that I use is the Donkey Kong Hacking Kit that contains a disassembly of the DK code.

The disassembly contains very useful comments on the internal workings of the DK code. When I started romhacking I scanned the disassembly to get a global understanding of the DK code. At first it is important to understand 1) the main game loop, 2) the important memory locations for keeping track of lives, levels, boards, etc and 3) the way the boards (girders and ladders) are defined and drawn.

When you start making changes another valuable source is the Z80 instruction set on Z80 Heaven. This is useful when you wanna know what an opcode exactly does (e.g. which registers are affected).

Editing the rom-files is possible with a hexadecimal editor, e.q. HxD.
Editing the sprite-files is possible with the Turaco Classic Sprite Editor.

To get you started you might look at my Donkey Kong romhacking site. The site contains a Hacking DIY section with tutorials for three very easy hacks that you can do yourself: 1) Change the Start Level, 2) Change the High Score Text and 3) Change the Bonus Item Sprites.

Hope this helps to get you started. If you have additional questions, feel free to ask.

Success with hacking

Paul

[Matt]

Would it ever be able to build you own daughter board that could run these rom hacks on a arcade cab?

[brett]

Would it ever be able to build you own daughter board that could run these rom hacks on a arcade cab?

Yes. The chips used in 1981 are very easy to read/write/replace by today's standards. Even things like Arduino can replace/emulate a ROM chip with a couple of simple parts on a breadboard!

[Matt]

How could I go about making my romhack, which isn?t made yet; just asking, programed onto a daughter board?