The NES needs a clock in order to function. Both the CPU and PPU use clock cycles to perform their duties. These chips run at different speeds, but each speed is derived from the same source – a 21.47727 MHz crystal on the NES motherboard. How do these components work in tandem?
This video dives into what cycles are, how they are used in the NES, how the CPU and PPU relate regarding the passage of time, and perhaps the most interesting bit for RetroRGB fans – why the vertical refresh rate of the NES is greater than 60Hz.
Hope you enjoy it!