The hearts of the Super Nintendo
When I start studying a vintage system, the first thing I like to do is to understand how its components work together at the hardware level[1].
Every computer has at least one heart which beats the cadence to all the other chips. Its CloCK output pin is connected to a copper line which spreads to most components, into their CLK input pin.
If you are mostly a software person like me, you may have never noticed it but all kinds of processors have a CLK input pin. From CPUs (Motorola 68000[2], Intel Pentium[3], MOS 6502[4]), to custom graphic chips (Midway's DMA2[5], Capcom CPS-A[6]/CPS-B[7], Sega's Genesis VDP[8]) to audio chips (Yamaha 2151[9], OKI msm6295[10]), they all have one.
The CLK can be generated by two types of components. One is a crystal oscillator which usually looks like a flattened capsule. The others are named ceramic resonators. These are vertical capacitor which look less high-tech than the crystals (and they also happen to drift over time).
With this in mind, let's peek inside a Super Nintendo. Can you find the CLK generators on a SNES motherboard? Clue: There are two.
