Plug them in, unplug them. No restarting required. The rumor on this is that IrDA is what the upcoming consumer portables will use to synchronize data with your desktop Mac. At 4Mbps, it's about 73 times faster than a 56k modem. With faster processors, you need a faster fan.
Processors give off a lot of heat.
However, if you have a fan that is rated for a 400MHz machine and your processor is only 300MHz, your fan may be running faster and thus be noiser than is needed. So, an automatic variable-speed fan keeps the processor running cool while keeping fan noise to a minimum. With the first generation G3 line, the processors have been much more powerful and flexible than the rest of the computer. This leads to a big bottleneck in performance. However, with the PowerMacintosh G3 Pro line due to be announced January 4th, Apple will raise the G3's performance capabilites by leaps and bounds.