e.g.: when you write the slp_typ register will trigger sleep smi.
after sleep smi done, it will rewrite the slp_tpy register to put system in Sx mode.
if system enable the IO Instruction Restart , after return the SMI, will automatic excute the command to slp_typ.
What's the IO Instruction Restart
原文：http://13143423.blog.51cto.com/13133423/1961121