2bt/chip-8 — pull request #1 by jimbauwens (2012-12-09 18:22:28+00:00)
Title: Fix for subtraction bug

VF got set incorrectly when subtracting (sub and subn).
This should fix a lot of issues you have with games.

Found this when porting this to the TI-Nspire. Games such as Brix didn't work properly, and after a lot of searching and decompiling Brix I figured out that this was the problem.
I made multiple other changes, but those are rather optimizations, so I'm not going to push that. This is needed for good emulator functioning.