CHIP-8 extensions and compatibility
This document is intended as a fairly exchaustive documentation of all extensions to CHIP-8. They all use the standard CHIP-8 interpreter as a base (including undocumented instructions, but not undocumented machine code routines), mentioning what additions and changes they make to that base.
This is mostly for historic purposes; few of the extensions listed here had a considerable number of programs written for them. Personally, my plan is to write an emulator that supports all of them. Perhaps the instructions listed here can inspire someone to make their own modern CHIP-8 extension as well (of which there have been a couple, see the bottom of the list).
It should also serve as a reference for the various incompatible instructions and behaviors that have cropped up in different interpreters over the decades.
The list builds on these documents: