Dan, Re: Wrong. That's not how it works. When you have a flat physical address space of a terabyte, you just map the devices like video cards and ports to starting addresses of, something like 256GB. Ram addresses from 0 to 4GB can stay just that - the hardware moves easily out of the way.
You might be right. I wasn't aware that this legacy requirement has gone away. Maybe that's part of the reason why Windows requires that drivers be rewritten for 64-bit mode.