Emulation is a difficult thing to do, particularly when you’re trying to emulate a complex platform like a game console, with little to no public documentation available. Often, you’ll have to figure things out by brute force and dumb luck, and from time to time everything will come unstuck when a random piece of software throws up an edge case that brings everything screeching to a halt.
The Classic NES series was a handful of Nintendo Entertainment System games ported to the Game Boy Advance in the early 2000s. What makes them unique is a series of deliberately obtuse programming decisions that make them operate very differently from other titles. These tricks utilize advanced knowledge of the way the Game Boy Advance hardware operates and appear to have been used to make the games difficult to copy or emulate.
The games use a variety of techniques to confuse and bamboozle — from “mirrored memory” techniques that exploit addressing anomalies, to putting executable code in video RAM and writing to the audio buffers in unusual manners.
Even more confusingly, these techniques only appear to have been used in the Classic NES series of games, and not other Game Boy Advance titles. It’s not obvious why Nintendo went to special effort to protect these ports over other titles; perhaps the techniques used were for other reasons than just an attempt at copy protection. Speculate amongst yourselves in the comments.
This isn’t the first time we’ve discussed emulation of Nintendo systems — check out this effort to reverse engineer the Sony Pocketstation.
[Thanks to [[[Codifies]]] for sending this in!]