Gentlemen, I have come across an issue using GCC 3.4.4 which I am in need of help. The problem manifests itself as extremely slow floating point performance for specific arguments passed to the dsin function in FORTRAN using g77. The following statement : y = dsin(dble(1.25169754E-06)) when compiled with g77 under GCC 3.4.4 will take 400usec to execute on my 2+ GHz Opteron platform. I have tested several machines and they all show the same problem. The same code executes at sub microsecond speed using GCC 4.0.2 on a Turion-64 notebook as well as a XEON based machine using gcc 3.3.3. Unfortunately changing the GCC version on my project is not an option. Can anybody shed some light on what is going on here ? Thanks for your help Fritz Jost