Hello gmp-4.2, gcc-4.1.2, Core 2 Duo -O3 -march=pentium-m -fomit-frame-pointer FAIL -fomit-frame-pointer -march=pentium-m GOOD -O2 -march=pentium-m -fomit-frame-pointer GOOD Does this mean that either gcc 4.1.2 or the CPU is buggy? Look at the Core 2 Duo bugs: http://www.geek.com/images/geeknews/2006Jan/core_duo_errata__2006_01_21__full.gif CL<