I saw an interview with one of the developers of ZSNES – one of the first truly great emulators. One of the key points, highlighted by PC Gamer and Time Extension was this great quote – how a developer achieved rollback netcode in 1997.
“30 times a second, I do a secret save state. The emulator plays ahead, maybe 30 milliseconds, and whenever it gets a packet saying the controller has changed, it rewinds to that frame and replays the emulation until the current point with that new input buffer.”
zsKnight – Zophar’s Domain Interview
Rollback netcode, even nearly 30 years later, is still a sticking point for many online games. It’s fine for first person shooters where you don’t need millisecond accuracy, but for things like fighting games like Street Fighter, it’s crucial. Really the only first enjoyable experience on fighting games online for me was Super Street Fighter II Turbo: HD Remix which was released in 2008, and even now the first thing many fighting game enthusiasts talk about was how it’s like to play online.
The fact that the problem was solved in 1997 before it is even a thing is so joyful.
I did manage to play ZSNES online in Business Studies class back in the day. Usually we were playing Bomberman or Mario Kart. Never got it working over dialup, but for a free version over a decent network, it is probably better than a lot of rollback netcode today.
You can watch the full (2 hour) interview below.