> After posting a previous message in the list, I got > the information that since my processor is a Intel > Pentium D (EM64T), I need to use amd64 as the target > during the compilation of GAMESS. However, it seems > like g77 for x86_64 machine doesn't work for compile > GAMESS, in this case. Why bother.. The Pentium D is a dual-core 32 bit chip with 64 bit extensions.. It's just a *bridge* to a real 64 bit chip. Compiling for 64 bit will gain you nothing in this case.