Emulation accuracy

How accurate the emulator is to the original hardware. Accuracy is most often achieved by tighter syncing. Less accuracy = less CPU power needed to emulate. More accuracy = more CPU power to emulate.

Levels

Low

• ZSNES

High

• Mednafen PSX

Cycle Accuracy

• bsnes
• Exodus
• CEN64

Circuit accuracy

Atari emulator that runs at 15fps on high end systems

http://sourceforge.net/projects/dice/

Controversy

There's controversy and debate about the exact level of accuracy needed.

Further reading

http://arstechnica.com/gaming/2011/08/accuracy-takes-power-one-mans-3ghz-quest-to-build-a-perfect-snes-emulator/

http://tasvideos.org/EmulatorResources/NESAccuracyTests.html