Original link: Intel optimizes slimmed-down X86S instruction set — revision 1.2 eliminates 16-bit and 32-bit features / Tom's hardware.
I don't think the article is good at explaining what the change actually means.
What will work: 64 bit application on 64 bit OS, 32 bit application on 64 bit OS.
What will not work: 32 bit application on 32 bit OS, 16 bit application on 32 bit OS.