ulfwald:
you left out BeOS in that list..
BeOS can utilize currently (i think) up to 16 processors, and in a dual-proc system will only waste 2-4% of the second processor, while an OS like windows NT will use-up 20% of the second processor just to manage the second processor... that's why under microsoft OS's a dual-600MHz machine won't give you the equivalent of a 1200MHz machine, but more like ~1000MHz...
-syf3r.