I got a 550 mHz motherboard for Ms Plant. It has huge electrolytic capacitors on it. I’ve seen this on fast boards at work. What’s the deal? They might need to regulate a lot of power, but why not do it in the power supply? There are five 2200 microFarad caps here.
The ROM sits right on the motherboard. Since, the ROM is on the motherboard, the capcitor needs to be there too to power it.
Also, the buses sit on the motherboard. When a bus changes state, the effects are additive, causing voltage spikes (I believe in the neighborhood of 300 to 500 mV) and also, 1 to 2 ms transients that develop on the power lines.
By plopping down some capacitors on the board, you’re able to keep the transients out of the power lines, and thus, the buses aren’t effected by the spikes. The capacitors absorb whatever voltage is left over.