Cheap, unreliable ceramic APU resonators lead to “constant, pervasive, unavoidable” issues.
Ideally, you’d expect any Super NES console—if properly maintained—to operate identically to any other Super NES unit ever made. Given the same base ROM file and the same set of precisely timed inputs, all those consoles should hopefully give the same gameplay output across individual hardware and across time.
The TASBot community relies on this kind of solid-state predictability when creating tool-assisted speedruns that can be executed with robotic precision on actual console hardware. But on the SNES in particular, the team has largely struggled to get emulated speedruns to sync up with demonstrated results on real consoles.
After significant research and testing on dozens of actual SNES units, the TASBot team now thinks that a cheap ceramic resonator used in the system’s Audio Processing Unit (APU) is to blame for much of this inconsistency. While Nintendo’s own documentation says the APU should run at a consistent rate of 24,576 Hz (and the associated Digital Signal Processor sample rate at a flat 32,000 Hz), in practice, that rate can vary just a bit based on heat, system age, and minor physical variations that develop in different console units over time.