You need some "Hardware 101" information.
> Try this excellent link:
FOR USB:
>
USB will never replace PCI; it can't. It is two entirely different hardware implemtations for your computer.
A computer will run without USB, it's an "addon" for periphreal devices.
A computer cannot run without PCI, nor can you use the same exact hardware in both.
Some are the same, and the USB interface allows you to use many of the same devices,
such as: modems, NIC - network cards, Printers, scanners Even hard drives, and others,,,,,,, but you can't hook up a Video card, or a Sound Blaster Live into a USB port.
USB was designed to replace the slow and clumbsy SERIAL PORT, with something MUCH faster, and that is PLUG & PLAY.
It is also,Hot swappable,,,,,, which offers one of it's best features.
USB Keyboards, and mice work great, and maybe a little smoother than PS/2 devices. However, that is not where you notice the difference, like when you use a Scanner or Printer, or a hi-perf Joystick / game controller...........
USB will transfer many, many more times the data (20X if I remember ........ probably more), and that means a lot to hardware and software that was really crippled by Serial Ports.
Hope this helps. All the info you could probably ever want, and more, is in those links I left above.