N64 Emulator RMG-K Brings Rollback Netcode to the Entire Library, Making Online Multiplayer Nearly Lag-Free

Reviving Classic N64 Multiplayer with Rollback Netcode

For fans of the Nintendo 64, the dream of seamlessly playing classic multiplayer games like Super Smash Bros. or GoldenEye 007 online has long been hampered by lag and input delay. While emulators have offered netplay features for years, the responsiveness often fell short of local multiplayer—until now. A recent update to the RMG-K emulator (a fork of the RMG N64 emulator) has introduced rollback netcode across the entire N64 library, drastically improving online play.

Released on May 14, the update brings rollback netcode to all N64 titles, though developer CigNus noted it is currently limited to two-player sessions. The implementation uses the GekkoNet framework, which has also been adopted in a fan project to port the PS2 version of Street Fighter 3: 3rd Strike natively to PC.

What Is Rollback Netcode and Why Does It Matter?

For those unfamiliar with the term, rollback netcode is a technology that makes fast-paced online multiplayer games feel responsive even on imperfect connections. Unlike traditional delay-based netcode, which waits for all inputs to arrive before displaying the result (causing noticeable lag), rollback predicts the next player inputs and corrects them when the actual inputs arrive. This minimizes perceptible delay and reduces desyncs. As demonstrated in a video shared by Bluesky user Grasluu00, players from Spain to Australia experienced only 4 frames of delay with rollback enabled—down from 9 frames without it.

Programmer NyxTheShield, who worked on the rollback features for RMG-K, stated on X that GekkoNet “did most of the lifting,” adding rollback “was honestly not that hard.” While coders often downplay the complexity, from an outsider’s perspective the technology remains almost magical in its ability to smooth out online play.

Technical Implementation and Initial Tests

The rollback implementation in RMG-K relies on the GekkoNet framework, designed to simplify adding rollback to emulators and game ports. NyxTheShield also posted footage of Smash 64 running smoothly with the new netcode, suggesting that even the most reaction-intensive N64 multiplayer games benefit greatly.

While it’s still early to gauge performance across every multiplayer title—the N64 has a library packed with classics like Mario Kart 64, Star Fox 64, and Perfect Dark—initial reports are promising. The reduction in input delay and desyncs is a significant leap forward for retro gaming enthusiasts.

Controversy Over AI-Assisted Coding

Despite the technical achievements, the RMG-K project has not been without controversy. The original creator of the RMG emulator, known as Rosalie241, publicly criticized the fork for its reliance on artificial intelligence in coding. In a Reddit post, Rosalie241 stated: “RMG-K is insulting, they took RMG's code, vibe coded changes with Claude and then have a donation button in the ReadMe of the project.” The developer expressed frustration that years of manual work were being leveraged by AI-assisted modifications, calling the situation “depressing and just sad.”

Coders involved with RMG-K, including NyxTheShield and CigNus, have referenced their use of AI tools in the past. This has sparked debate within the emulation community about the ethics of using large language models for code generation and whether it undermines the effort of original developers.

Looking Ahead: The Future of N64 Online Play

The addition of rollback netcode to RMG-K is a major milestone for N64 emulation. It opens the door for competitive online play in games that have been limited to local multiplayer for decades. While the project is still evolving—with plans to potentially extend support beyond two players—the current implementation is already a game-changer. For fans of the N64, now is an excellent time to dust off their ROMs and enjoy a genuinely lag-free online experience.

As the emulation community continues to refine rollback technology, the line between local and online multiplayer will blur further. RMG-K may be just the beginning of a new era for retro gaming on the internet.