I'm looking to allow two cartridges to be inserted into a slot that normally only accepts one (more specifically, Nintendo 64 cartridges). I can't just toggle the power lines to each cartridges because of backfeeding. What sort of device would I need to use to switch a large number of lines from one cartridge to another (an N-pole single throw relay)? In this case, there isn't much power passing through the lines, but in a more general sense what component would one need to actuate multiple switches in a near-simultaneous timeframe?
The ADG3300 is usually used as a voltage translator, but will work fine with the same voltage on both sides. Pulling the EN input low tristates the Y pins (on the inside) and pulls down the A pins (on the cartridge), virtually disconnecting the two sides from each other. A couple of power MOSFETs will allow you to control V+ and GND.