To owners of AMD64 motherboards whose BIOS offers options for S/W Memory Remap and H/W Memory Remap:
E Stepping and later Athlon 64 and Opteron processors can manage the memory remap scheme in hardware. If your processor is E stepping or later, enable H/W remapping but you can leave S/W remapping disabled.
If your processor version is earlier than E step (CG), it cannot manage the memory remap scheme in hardware (but does partially), so you should enable S/W remapping. Enabling H/W remap will be of no benefit to you.
As I understand it, in either case, you must have a 32-bit OS that can do 36-bit PAE or a pure 64-bit OS, or you run the risk of breaking 32-bit software and device driver compatibility. Feel free to correct me if I'm wrong.
E Stepping and later Athlon 64 and Opteron processors can manage the memory remap scheme in hardware. If your processor is E stepping or later, enable H/W remapping but you can leave S/W remapping disabled.
If your processor version is earlier than E step (CG), it cannot manage the memory remap scheme in hardware (but does partially), so you should enable S/W remapping. Enabling H/W remap will be of no benefit to you.
As I understand it, in either case, you must have a 32-bit OS that can do 36-bit PAE or a pure 64-bit OS, or you run the risk of breaking 32-bit software and device driver compatibility. Feel free to correct me if I'm wrong.