Probably I made some mess in my word.. I tested the speed in two way: First: I compile the program on a P3(1 Ghz) and I copy it on a P4 (2.4 Ghz) also. In this way the executable is the same (Byte per Byte), but I see that the speed on P3 is faster (!!!) than the P4. Second: I compile the program on P3 and run it. I compile the program on P4 and run it. I see that the P3 is faster than P4. The P3 is faster than P4. Why? (Very strange) I didn't install any special program and I have made some tests on different P4. E.G.