Very good article. I work on BIOS for a living, and I have to give this explanation to testers all the time.
Which platforms are mote likely to support remapping over 4GB … servers. Most desktops and notebooks won’t support it.
If the memory controller will support remapping memory above 4GB, then you’re fine. The “memory hole” will get pushed up over 4GB. If not, then you lose that memory to all of the PCI devices on the system.
On AMD Athlon/Turion/Opteron platforms, the memory controller is in the CPU. On Intel platforms, this is the MCH/GMCH (also called a “northbridge”).