Overclocking is the process by which the CPU clockspeed is increased. The reason for doing this would be to reduce slowdown in games, or to increase the framerate. However, as this is a hack and not intended by designers, it can result in many issues. Certain systems can have an overclocked CPU with few if any issues, while others can not overclock without major issues.
|System||Normal clock||Hardware Overclock||Emulation Overclock||Overclock levels|
|SNES Main CPU||3.58 MHz||Yes||No||4.1 -7.6 Mhz|
|SNES SFX1||10.5 MHz||Yes||Yes||40-60 Mhz|
|SNES SFX2||21 MHz||Yes||Yes||40-60 Mhz,|
|Sega Genesis||7.7 MHz||Yes||Yes||13.1-25.4 MHz|
|Sega Saturn||28.6 MHz*||No||No||-|
|Nintendo 64||93.75 MHz||Yes||Yes||125-187.5 Mhz|
|Neo Geo||12 MHz||Yes||Yes||14-18 MHz|
*Sega Saturn has two SH-2 CPUs
Overclocking is possible on real hardware, but doing so also speeds up the audio. No NES emulator allows overclocking.
The main SNES CPU ran at 3.58 MHz and can be overclocked. However it causes issues. With those who have tested it, the following issues occur:
- "4.1 MHz: Small amounts of sprite breakup occasionally; very little slowdown.
- 5.1 MHz: Sprite breakup; no slowdown
- 6.6 MHz: Color palette errors; sprites fail to render
- 7.6 MHz: Color palette errors; sprites fail to render. Freezes after a few minutes."
There are no SNES emulators that allow for an overclocking option, likely because of those issues.
The first version of the chip, commonly referred to as simply "Super FX", is clocked with a 21 MHz signal, but an internal clock speed divider halves it to 10.5 MHz. Later on, the design was revised to become the Super FX GSU-2; this, unlike the first Super FX chip revision, is able to reach 21 MHz.
The SFX chip however can be overclocked with fewer issues on real hardware or emulation. It does however increase the speed of the game as well.
Tests have shown that overclocking can increase the speed of the game, in addition to increasing the framerate and removing slodown.
Overclocking the main CPU also has the effect of speeding up the audio as well.
Some games (see the list below) can take advantage of overclocking and improves framerate, while most others (such as Super Mario 64) have built-in framerate limiter and unaffected by overclocking.
List of games that can take advantage of overclocking
A Bug's Life Aidyn Chronicles - The First Mage Armorines - Project S.W.A.R.M. Big Mountain 2000 Conker's Bad Fur Day Destruction Derby 64 Disney's Donald Duck - Goin Quackers / Donald Duck - Quack Attack Duck Dodgers Starring Daffy Duck / Looney Toons - Duck Dodgers Earthworm Jim 3D Extreme-G Extreme-G XG2 F1 Racing Championship F-1 Pole Position 64 Gex 3 - Deep Cover Gecko Goldeneye 007 Hot Wheels Turbo Racing Human Grand Prix - New Generation Jet Force Gemini / Star Twins Jeremy McGrath Supercross 2000 Kobe Bryant's NBA Courtside Madden Football 64 Madden NFL 99-2002 Milo's Astro Lanes Monaco Grand Prix - Racing Simulation 2 Monster Truck Madness 64 NASCAR 99/2000 NBA In the Zone 98 / NBA Pro 98 Off Road Challenge Perfect Dark Quake II Racing Simulation 2 Rakuga Kids Rayman 2 - The Great Escape Roadsters Trophy South Park Rally StarCraft 64 Starshot - Space Circus Fever Super Robot Spirits Taz Express Tom Clancy's Rainbow Six Tonic Trouble Toy Story 2 Transformers - Beast Wars Transmetal Turok 2 - Seeds of Evil / Violence Killer - Turok New Generation V-Rally Edition 99 WCW vs. nWo - World Tour World Cup 98
Dolphin supports overclocking and underclocking the CPU. Overclocking can remove slowdown from games that have them, pushing them closer to their actual target frame rate. It causes several issues with many games, so don't expect it to be a perfect solution.
Dolphin used to have a VBeam Speed Hack that doubled GPU clock rate. This has since been removed, as the developers found that it didn't really help in any cases.
On original model PS2s you can overclock by a small amount without too much problem, the biggest issue will be sped up audio. Slim model PS2s use the GPU's clockrate as a base for the CPU (multiplying the GPU's clock by 2), so overclocking the CPU will also overclock the GPU resulting in many visual problems.
PCSX2 uses the CPU clock as a base and divides for GPU clockrate, so overclocking will result in visual problems too, as well as sped up audio. PCSX2 OC Builds. The emulator also has a speed hack called VU Cycle Stealing, which allows for increased GPU performance at the cost of CPU cycles. It gives an incorrect FPS readout, though.
PPSSPP allows over/underclocking of the main CPU. Due to Sony underclocking the CPU to 222 MHz then removing the underclock in a later firmware update to allow it to run at 333 MHz (and thus not having games closely tied to clockrate), overclocking the system (and emulating an overclocked system) results to next to no ill effects.
Final burn alpha allows for overclocking of Neo Geo games. MAMEUIFX (aka MAME32FX) also allows for overclocking. All Neo Geo should run at full speed when overclocked.
The original hardware can be overclocked leading to faster/smoother gameplay. 
Regen allows overclocking in the dev build version. Games with sprite flicker, like Altered Beast, and games with slowdown, like Rambo III or Mega Man: The Wily Wars, play perfectly with Regen's "Overclock M68000" setting at 732 (1.5x original speed). The game speed and audio are unaffected by overclocking.
- When you overclock the CPU, the audio speeds up as well.