“Blast processing” in 2019: How an SNES emulator solved overclocking

When it comes to emulator design, there's something to be said for trying to capture the workings of the original system as accurately as possible, warts and all. But there's also something to the idea that emulators can improve on the original hardware, smoothing problems like frame rate slowdown that plagued the underpowered processors of the day.

That brings us to the latest update for storied, accuracy-obsessed SNES emulator bsnes, which adds the ability to overclock the virtual SNES processor. While bsnes is far from the first SNES emulator to allow for simulated overclocking, it does seem to be the first that does so "without any framerate or pitch distortion, and without harming compatibility in 99% of games," as bsnes programmer byuu puts it.

Fast, but not too fast

Most SNES games were locked to a 60fps frame rate, and designers of the time tuned their games so the SNES hardware could maintain that frame rate. But in some in-game situations, when the screen got too full of moving sprites, the processor could fail to create the next frame within the 16.66 ms window, leading to noticeable display lag.