So. Mega Man X2 and X3, right?
The only two games known to use the CX4 expansion chip, for a bunch of different stuff involving wireframe model rendering, trigonometry, all sorts of maths.
That's all cool and good.
But then someone wrote a homebrew snowball fight game that used the CX4's math functions to correctly toss those snowballs.
It worked fine on any SNES emulator that supported Mega Man X2, so basically any one of them at the time. And you might think if you sacrificed an MMX2 PCB to put that snowball game on it, it'd work on the original hardware, too.
As it turns out, "the CX4's math functions" is a misunderstanding. The CX4 had no math functions, or wireframe drawing functions, or anything at all.
The CX4 was not a fixed-function device.
MMX2 and X3 could use it to do all these things because in their own ROMs there was a block of CX4 specific code that would be copied in there on boot.
The snowball game was written before this was discovered, so it never did any of that and ended up calling math functions unknown to the device.
Sad, isn't it?
