bsnes had already made news back in April with its well-received HD Mode 7 mod, however, it looks like a new retrogame enhancement feature will soon be added to its arsenal. Overclocking is now available in the emulator's nightly builds and, while it's true that other emulators have included it a long time ago, this implementation is severely different from the others in many ways.
Byuu, the developer behind bsnes, has explained the feature accurately in a Reddit post. Unlike before, where fixed overclocking could introduce sound/framerate issues or crashes in some games, this new method's goal is to counter slowdowns without any audiovisual compromises while also keeping compatibility as high as possible. The inspiration came from a technique already used in NES emulators, where more scanlines would be inserted in the CPU thread while pausing video and audio in the meantime; and everything described so far can also be used with the SA-1 and SuperFX coprocessors (others don't need it as they're implemented via HLE). The end result can be seen in the videos below, and it really speaks for itself (also, while not showcased in the videos, this method is also compatible with HD Mode 7!)
However, byuu warns users to keep overclocking settings to reasonable levels, otherwise, it can have an adverse effect on resource usage (if set too high, you will likely end up wasting CPU cycles between frames for no reason). As such, mitigations or limits for popular games are reportedly being experimented with at the moment.
As previously mentioned, the feature is available in bsnes' nightly builds and will be officially added in the next stable release. The same implementation has also been picked up by a different, relatively new SNES emulator, Mesen-S. There's a high chance it will also be ported over to the respective Retroarch/libretro cores sometime in the future.
Source (bsnes \ Mesen-S)