Frames per second

There are two distinct types of "frames per second" to consider when discussing emulation: virtual (output) FPS and real internal FPS.

Virtual (Output) FPS

Virtual FPS represents the rate at which the emulator outputs video frames to match the display standard of the original console's video encoder. Historically, this was dictated by regional television broadcasting standards: NTSC (USA, Japan): Outputs at 60 FPS (technically 59.94 Hz). PAL (Europe, Australia): Outputs at 50 FPS. In later console generations, like the GameCube and Wii, many PAL games included a "PAL60" mode, allowing them to output at 60 FPS. In an emulator, maintaining this virtual FPS simply means the software is successfully decoding the video signal and refreshing the screen at the correct native frequency. It does not necessarily mean the game itself is running smoothly.

Real Internal FPS

The real internal FPS is the actual rate at which the game engine updates its logic, physics, and rendering pipeline. With the transition to 3D graphics, maximizing internal frame rates became incredibly demanding on original console hardware. While the console might still output a continuous 50Hz or 60Hz virtual signal to the television, the game engine itself often ran much slower: Most early 3D games targeted an internal 30 FPS. Some intensive titles ran even lower. For example, The Legend of Zelda: Ocarina of Time runs at an internal 20 FPS in NTSC regions, and just 17 FPS in PAL regions. Star Fox runs below that.

The Emulation Challenge

Achieving a stable virtual FPS is relatively easy for modern hardware. However, replicating the real internal FPS requires highly accurate emulation of the original console's timings, CPU bottlenecks, and sub-processor interactions. If the emulation lacks accuracy, the internal frame rate can fluctuate wildly, or the "guest/emulated" game engine can overperform. For example, a game like Grand Theft Auto IV on the PS3 famously hovered around an average of 24 FPS due to real hardware strain. An emulator lacking accurate timing constraints might brute-force the engine to run at a flat 30 FPS. While a higher frame rate sounds like an upgrade, it fails to replicate the authentic, historical console experience. To truly emulate a system, the software must accurately mimic the original hardware's struggles. Modern emulators introduce specific accuracy toggles for their recompilers. For example, DuckStation include an option called "Enable Recompiler ICache" for their MIPS recompiler. When enabled, it deliberately simulates instruction cache misses and CPU stalls, forcing the recompiler to match the hardware's native timing constraints and keeping the internal frame rate authentic to the original console.

Frametime stability vs avg FPS

Frametime stability

Prioritizing other aspects of the game over high frame rates peaked during the seventh generation with the Xbox 360 and PlayStation 3. Even though many titles heavily relied on lower internal rendering resolutions and upscaling to reach a target 720p output, they still often suffered from low frame rates (which popularized the "cinematic 24FPS experience" meme during that era). When analyzing both retro and modern software, however, frametime stability (the consistency of the delay between consecutive frames) is often more critical to the perceived smoothness of a game than its peak or average frame rate. A rock-solid, properly paced 24 or 30 FPS with consistent 1% and 0.1% lows will provide a vastly smoother visual experience than a fluctuating 60 FPS target plagued by erratic frame pacing and micro-stutter.

Slowdown

If you are experiencing a slowdown on emulation speed (lesser than 100%), it may be that the emulation is too intense for your system. When this happens, both the video and the sound experience slowdown. To counteract this, you can enable speed hacks, use a less intensive emulator/settings or get new hardware particularly the CPU. However, if the slowdown only affects the internal FPS (frames processed per second within the emulated system), it likely reflects the original game's behavior and accurately represents the limitations of the original hardware. In such cases, there is nothing can be really done for this, other than overclocking the virtual hardware or reprogramming the game itself. This type of slowdown often affects video while audio remains unaffected, and the displayed emulation speed will still be 100%.

Audio hitching or stuttering

Some emulators implemented various workarounds for audio issues especially caused by slowdowns. See Granule Synthesis Audio System section in dolphin-emu.org/blog/2025/06/04.

Frame pacing

See frame pacing improvements section in dolphin-emu.org/blog/2025/06/04.

Overclocking

Main article: Overclocking

Speed hacks

Using speed hacks can affect both types of FPS in emulators. Most of these are used to alter emulation, sacrificing accuracy for speed to help achieve 30FPS/60VPS. Some speed hacks, however, can lower the internal FPS to raise the emulator's output FPS; an example of this is in PCSX2, known as EE cycle stealing, which reduces the clock speed of the virtual CPU used, the Emotion Engine.

There are a few game hacks that optimize game code in order to remove possible instances of in-game slowdown. There also exist a few speed hacks that increase a game's internal frame rate. They only function properly in emulators with overclocked hardware.

60 FPS cheat codes

Main article: 30/60 FPS cheat codes

These are speed hacks in the form of cheat codes affecting the game's internal FPS for games running at 30 FPS to get them to play at 60 FPS. However, these are often game-specific and very prone to bugs considering many of the games weren't made with 60 FPS in mind. Notably, the walking speed and animations might play at double speed, which can cause some gameplay problems like for example, making a mission impossible to beat in Metal Gear Solid: Peace Walker because the enemies are too fast.

Frame generation technology

Main article: 30/60 FPS cheat codes