How Early Video Games Synchronized Gameplay Over Modems

A 1998 patent describing a method to keep two remote video games in sync by exchanging command signals and timing codes over a modem connection.

What it covers

This patent describes a hardware assembly that sits between a video game console and a modem to enable remote multiplayer gaming. It captures player inputs (like button presses) from the local console and receives similar inputs from a remote player via a data link. A synchronizer component then ensures these two sets of inputs are fed into the game's processor at the same time. It also uses a counting mechanism to track when the game states drift apart; if the synchronization codes don't match for a set number of cycles, the system retrieves stored player parameters to re-align the games.

What it doesn't cover

• —Does not cover modern high-speed internet multiplayer architectures that rely on server-side state reconciliation.
• —Does not cover wireless or Bluetooth-based controller synchronization.
• —Does not cover cloud gaming where the game logic runs on a remote server rather than a local console.
• —Does not cover synchronization methods that do not utilize a specific local and remote synchronization code comparison.

The clever bit

Instead of trying to sync the entire game state (which was too much data for 1990s modems), it only synchronizes the input commands and uses a counter to detect when the two consoles have drifted out of sync.

Why it matters

This patent represents an era when developers were solving the fundamental problem of 'lag' and state divergence in early dial-up multiplayer gaming. It highlights the transition from local-only play to the networked experiences that define modern gaming, specifically addressing how to keep two consoles running the same game logic simultaneously over slow, unreliable phone lines.

Real-world examples

• 1.Early dial-up modem adapters for 8-bit and 16-bit consoles
• 2.Peer-to-peer multiplayer configurations for early PC gaming
• 3.Modem-based game link peripherals