Requirements

Hard Requirements

• HTML5 Canvas API for display
• WebAudio or Moz Audio Data API or Flash Plugin for audio.

Semi-Hard Requirements

• Typed Array API support.
  • Won't really run well at all if it's not supported.
  • It's shimmed, but has fast paths that are effectively necessary.
• Audio
  • The flash fallback is subpar and doesn't work well on most browsers.

Multi-threaded Emulation

• Webworkers for thread creation
• SharedArrayBuffer API for cross thread communication.
• Futex/Atomics API that was written with the SharedArrayBuffer API.
  • Due to Spectre/Meltdown this is disabled by default in recent browsers. It can be re-enabled manually in most.

Full Speed Runtime

• Firefox ~38+ & Safari 10.1+
  • With Multithreading
    • 2.4ghz Core 2 Duo
    • 1.2ghz Skylake CPU
  • Without Multithreading
    • 2.8ghz Core 2 Duo
    • 1.4ghz Skylake CPU
• Google Chrome
  • With Multithreading
    • 3.6ghz Core 2 Duo
    • 1.8ghz Skylake CPU
  • Without Multithreading
    • 4.2ghz Core 2 Duo
    • 2.1ghz Skylake CPU
• MS Edge
  • With Multithreading
    • 2.6ghz Skylake CPU
    • Only mode that properly produces audio, as Edge as some threading bug!
  • Without Multithreading
    • 3.0 ghz Skylake CPU
    • Bug in edge glitches audio at medium(near 60%) CPU load.

Yes, you're reading it right, Skylake (6700k) CPUs are twice as fast as Core 2 Duo (P8600) CPUs at the same clock speed running this emulator. Firefox as old as version 4 can run this, but I don't recommend anything older than version 25 to get within 80% speed of the latest firefox. Safari versions older than 10.1 get exponentially slower for each version further back you go.