Judging from what i see people do on a couple of OG Xbox Discord rooms, i'd guess the biggest contributor would be reverse engineering the existing software (g

Judging from what i see people do on a couple of OG Xbox Discord rooms, i'd guess the biggest contributor would be reverse engineering the existing software (games, etc) using tools like Ghidra (and whatever was common for reverse engineering before it). After that you build a bunch of tests that you can try to run on the original hardware and compare with the emulator (e.g. this[0] repository contains a bunch of tests written against the open source nxdk SDK for the original Xbox - note that the effort goes back to very early 2000s and it is only in recent years that you could call it usable for more than basic things[1] - and the author often contributes tests to specific issues with the Xemu emulator[2] comparing it with the real Xbox). [0] https://github.com/abaire/nxdk_pgraph_tests https://github.com/abaire/nxdk_pgraph_tests [1] though nxdk/freexdk/openxdk had to "compete" with the leaked XDK that a lot of homebrewers used so there was much less incentive to contribute to the open source one [2] https://xemu.app/ https://xemu.app/