Existing SNES emulators sometimes allowed overclocking the SNES CPU by a fixed amount, but it was done in a way that would either increase the video and audio rate, or break games.



bsnes and Mesen-S now feature a new way of overclocking that comes from the NES emulation scene: inserting additional scanlines into the CPU thread, without running the video and audio during this time. The result is a method of removing slowdown in just about any SNES game, without any framerate or pitch distortion, and without harming compatibility in 99% of games (even streaming audio games such as Tales of Phantasia work as expected.)



The SA-1 and SuperFX can also be overclocked in this way. The other coprocessors (DSP-1, Cx4, etc) support HLE which results in all of their operations occurring instantly, so it didn't seem useful to add overclocking to them.