Different processor types is my guess, Martin. Math coprocessing, L2 cache, memory handling, and I probably have forgotten something...
Anyway, the tweak likely works best on some of the older single core cpus and you probably don't need it on yours, as Peter has indicated.
I follow the old pilot's method, get some altitude and throw the stinkin' switch. if it don't do nuthin', throw it back the other way real quicklike and hope your backseater didn't notice...
--Mac