> Why didn't you follow the advice you quoted? > gcc -march=pentium4 -mfpmath=sse > When you compile code for pentium2, of course SSE is not available to > the compiler. Thank you very much. gcc -march=pentium4 -mfpmath=sse seems to work correctly. The threshold is now 1.5*2^{-52} as it should be. I did not try -march=pentium4 before, since man gcc contains several descriptions of -march for each architecture class separately and I did not reach the right one. Thanks to all of you, who send me advice. Petr.