Overclocking

From Emulation General Wiki
Revision as of 19:38, 8 April 2014 by 173.206.82.252 (talk) (Mega Drive)
Jump to navigation Jump to search

WORK IN PROGRESS. Article is not finished, and information is not complete. Please expand.

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.

Chart

System Normal clock Hardware Overclock Emulation Overclock Overclock levels
NES 1.79 MHz Yes No ?
SNES CPU 3.58 MHz Yes No ?
SNES SFX1 10.5 MHz Yes Yes 40-60 Mhz
SNES SFX2 21 MHz Yes Yes 40-60 Mhz,
Mega Drive 7.7 MHz Yes[1] No 13.1-25.4 MHz[1]
PlayStation 33.8 MHz Yes[2] No 66Mhz[2]
Sega Saturn 28.6 MHz* No No -
Nintendo 64 93.75 MHz Yes[3] Yes 125-187.5 Mhz[3]
Neo Geo 12 MHz Yes[4] Yes 14-18 MHz[4]

*Sega Saturn has two SH-2 CPUs

Famicom (NES)

Overclocking is possible on real hardware, but no emulator allows for it.

SNES

Main CPU

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."[5]

There are no SNES emulators that allow for an overclocking option, likely because of those issues.

SFX chip

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.[6]

Clock speed Time Increase
Normal 1'46'02 -------
50hz 1'23'78 27.711%[6]

Snes9x-Next allows for SFX overclocking.

PC-Engine (TG-16)

Overclocking the main CPU also has the effect of speeding up the audio as well.[7]

N64

Mupen64Plus - VI Refresh

GameCube/Wii

Dolphin - VBeam Speed Hack doubles GPU clock rate.

PS2

PCSX2 - VU Cycle Stealing allows for increased GPU performance at the cost of CPU cycles.

Neo Geo

Final burn alpha allows for overclocking of Neo Geo games. All Neo Geo should run at full speed when overclocked.

Mega Drive

The original hardware can be overclocked leading to faster/smoother gameplay. [8]

No MegaDrive emulator currently supports overclocking.

The Genesis Plus GX dev says that implementing overclocking is "not easy to add without potentially break other things. "[9]

References