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| Has there ever been a documented reverse engineering of an arcade game? |
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| jimmy2x2x:
--- Quote from: RayB on March 11, 2012, 02:39:18 pm ---Guys, even coding for for the 16bit systems was generally done in Assembly. We're talking 1mhz machines. You had to squeeze out every bit of juice possible and manipulate data directly at the bit level. --- End quote --- Not to undermine anyone else, but you are talking a lot of sense here and this is my impression of that era too. |
| lilshawn:
see, everyone is stuck in "today thinking". back in the day they just wrote the programs and controlled the CPU directly. there is no coding in c+ and compiling it, there is no FORTRAN...nothing. no compiling there is no assembing of laguage at all. Everything is/was straight machine language. you needed information from a register, you sent the command and the CPU spit out the contents of the address. inherently machine code makes absolutely no sense... this is why there is no reverse engineering of the original code. it becomes a mish mash of commands randomly reading and writing to registers. it's all there but only once the program runs does the outcome show whats going on. In the Z80 the machine code 00000101, which causes the CPU to decrement the B processor register, would be represented in assembly language as DEC B. the 00000101 gets lost in the stream of other commands and makes it impossible to "see" i'd like to compare it akin to a plain box full of puzzle pieces but even that doesn't seem fitting. |
| Gray_Area:
Following up this topic, I came across this: Anyhow, you might be curious about how I actually went about developing this. Seeing as I'm not a CAVE employee, I don't actually have the source code. Instead, I relied on my competancy as a reverse engineer to find all of the things I needed to change in order to make the game mechanics how I want. Now, you might assume I used a compiler, or even an assembler. You'd be dead wrong! I wrote out the assembly code I wanted to insert, then I referred to the M68000 User Manual to manually assemble every instruction. http://dodonpachi.daifukkat.su/ddpa/ |
| pwrx:
Ancient post but just seeing this site... There are just a few 'fully' reverse engineered arcade machines. By this I don't mean selective commenting on sections of the source code, rather the purpose of every last byte 100% known, all interaction with routines, memory locations documented with variable names, internal state machines documented - pseudo intenal languages known with tools to compile/decompile that too. Result being code that is largely relocatable, and easily modifiable but initially can produce byte-matching roms. I spent a huge amount of time working on Gauntlet II and only got about 25% through. I did go all the way with Omega Race some time ago. This one is without a doubt written in assembly and for the most part every byte / cycle counted. It was pretty clear though that they had a sound effect team and programming team that didn't spend enough design time together. Lol. |
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