Note that this doesn't enable you to run 64-bit applications, or for any single process to address more than 4GB of memory.
As a result, it's of extremely limited utility today - you'd need a 32-bit application that needs to run on bare hardware (ie, not a 32-bit OS running under a 64-bit VM), and needs a ton of memory, or a pre-64-bit system with > 4GB of memory, which would be both rare and inefficient, as that would be single core/socket systems that are at least 6 years old at this point.
I guess if you had some system you were trying to keep alive that needed a lot of RAM, PCI-X card slots, and 32-bit software it might be handy, but that seems very rare/esoteric at this point.
As a result, it's of extremely limited utility today - you'd need a 32-bit application that needs to run on bare hardware (ie, not a 32-bit OS running under a 64-bit VM), and needs a ton of memory, or a pre-64-bit system with > 4GB of memory, which would be both rare and inefficient, as that would be single core/socket systems that are at least 6 years old at this point.
I guess if you had some system you were trying to keep alive that needed a lot of RAM, PCI-X card slots, and 32-bit software it might be handy, but that seems very rare/esoteric at this point.