It is in the game configuration options as "Frameskip - Skip Every xx Frames".
Star Fox gets a pretty good speed bump that makes it almost full speed. There is one for Super Mario World as well, although I don't remember that game having speed issues. Star Fox and variants, Vortex, Super Street Fighter II, FF 6 & 3, Chrono Trigger ). Some of them provide noticeable speed improvements others I'm not sure (maybe in certain parts of games). Implemented several speed hacks from the retroarch core (applies to 1.53 and 1.51).
However it can make text unreadable in some games. This helps improve speed in games that uses the SNES hi-res mode (Jurassic Ppark and Super Bases Loaded 1 & 3). so using the left analog as a lightgun is rather difficult. Note: 1.43 core does not display a crosshair.