While trying to nail down the last few bugs in my own chip-8 emulator I consulted other emulators on github (there are tons). Weirdly, some instructions behave

While trying to nail down the last few bugs in my own chip-8 emulator I consulted other emulators on github (there are tons). Weirdly, some instructions behave slightly differently with every emulator. I found this guide to be the most complete one and hence thought it's worth bringing up. However, I could not find consensus on what "borrow" means for the SUB instructions (8XY5 and 8XY7) - most implementations set the borrow bit even when the two operands are equal.