Chip-Eight Hacking Emulator

[Abystus]

I glad really you posted this Abystus, I've never even heard of the Chip 8 TBH. And the ROMs are not even half a kilobyte. Now I know of yet another system I've never even heard of, thanks!

No problem. Hopefully your able to make some hacks for it (I haven't seen anything for this system before this point in the way of "hacks", though I'm not sure anyone really thought to do so with such simple games.), and possibly give the emulator a good run through for bugs at the same time.

[47iscool]

No problem. Hopefully your able to make some hacks for it (I haven't seen anything for this system before this point in the way of "hacks", though I'm not sure anyone really thought to do so with such simple games.), and possibly give the emulator a good run through for bugs at the same time.

I'll try, I have one ROM called Car Race V1.00 so far. Could you tell me what value represents an nop instruction for this system?

[Mezmorize]

Well, there are several ways that walking bounds are programmed. Though I find the simplest method is to start by seeing if a new value is being written when you touch a wall (no trace). If so, go after that write with a wp/trace. If no new value is written when touching the wall, and all writes either repeat a value or stop writing all together, try looking for a branch over somewhere above that area. Things can get tricky, though there are several tools to help pinpoint branches (ahem BranchFinder) which may simplify this task. I've haven't had the need for a WTW in mess or mame as of yet, and have really only made them in FCEUX and Geigers Snes9x. Also, as pugsy describes in that post, you can ignore certain writes to an address, thus allowing you to easily see what is "stopping" your progression in a direction if it is a forced value type. A few different variations (something I wrote a while back) that may apply to certain games you will encounter can be found here.

Thanks for your detailed info, I'll have to give it another shot sometime soon.
Thanks for your BranchFinder tool by the way, I use it all the time, and I don't think it gets the recognition it deserves.
As far as Pugsy's info about ignoring writes, It's the reason I bookmarked the thread, I didn't know of that feature until I read it there and I love that feature.

Thanks for all the hard work you do for us, and your excellent programs!

[47iscool]

Thanks for all the hard work you do for us, and your excellent programs!

I second that.

[Abystus]

I'll try, I have one ROM called Car Race V1.00 so far. Could you tell me what value represents an nop instruction for this system?

I don't believe this is a NOP in this instruction set. If you can creatively change the instruction to something else (Example Jump to Address to a different address, or a Skip if Equal to Skip if Not Equal) then it's great. If you find yourself in a pickle, and can't find a good replacement for what your stuck on then change the opcode to a 00 (though be careful the operand isn't a 0xC0 (SuperChip - Scroll Down), 0xE0 (SuperChip/Chip8 - Clear Screen), or 0xEE (SuperChip/Chip8 - Return) in the original instruction, or you could possibly run into problems). This emulator handles "Unknown" instructions as invalid no operation types, and since this isn't really an actual system (that has a hardware counterpart), I'd say go for whatever you can get working.

[47iscool]

I'll just have to play around with it as everything else I've learned to hack with, I also didn't know the chip 8 was a handheld. It also wows me that someone can create a program of only 320 bytes...amazing.

[OldSchoolGamer]

Awesome, it looks nice!
I had never even heard of the 'system' before.
It's a pity more games weren't programmed for it.

Me too... the whole time reading the article, I was thinking, WTF is Chip-Eight?... contemplating whether to pause from reading and Google/YouTube it.

That's pretty impressive man. I look forward to checking it out further.

[Abystus]

I'll just have to play around with it as everything else I've learned to hack with, I also didn't know the chip 8 was a handheld. It also wows me that someone can create a program of only 320 bytes...amazing.

Well chip-8 was more of a virtual machine used to test games running on the microcomputers of the time. It has since been ported via software and hardware emulation to a lot of different platforms. I think anyone wanting to start out ROM hacking could most likely make a start with this system as it has very few instructions to get confused with (also every instruction uses 2 bytes aligned). I hack it on and off now that I can (with these tools), though the games aren't really mainstream enough to get attention (unless something crazy is found lol).

[Mezmorize]

I never heard of Chip 8 before, now I'm seeing it everywhere.
OK maybe not everywhere, but I randomly ran across it while looking at some stuff at SMSPower.
http://www.smspower.org/maxim/SMSSoftware/Chip8

You likely already knew about it though.