Hello, in the last days I ran a simulation on a x86_64 architecture: ################### processor : 0 vendor_id : GenuineIntel cpu family : 15 model : 6 model name : Genuine Intel(R) CPU 3.20GHz stepping : 8 cpu MHz : 3192.081 cache size : 8192 KB physical id : 0 siblings : 2 core id : 0 cpu cores : 2 fpu : yes fpu_exception : yes cpuid level : 6 wp : yes flags : fpu vme de pse tsc msr pae mce cx8 apic sep mtrr pge mca cmov pat pse36 clflush dts acpi mmx fxsr sse sse2 ss ht tm syscall nx lm constant_tsc pni monitor ds_cpl vmx est tm2 cid cx16 xtpr lahf_lm bogomips : 6390.34 clflush size : 64 cache_alignment : 128 address sizes : 40 bits physical, 48 bits virtual power management: ##################### with very poor performance. I ran the same simulations on my notebook: ###################### processor : 0 vendor_id : AuthenticAMD cpu family : 6 model : 8 model name : mobile AMD Athlon(tm) XP 2000+ stepping : 1 cpu MHz : 797.820 cache size : 256 KB fdiv_bug : no hlt_bug : no f00f_bug : no coma_bug : no fpu : yes fpu_exception : yes cpuid level : 1 wp : yes flags : fpu vme de pse tsc msr pae mce cx8 sep mtrr pge mca cmov pat pse36 mmx fxsr sse syscall mp mmxext 3dnowext 3dnow ts fid vid bogomips : 1596.37 clflush size : 32 ####################### The same simulation is about 10 times faster on my notebook. The simulation was compiled with "-O3 -ffast-math", without "-ffast-math" the performance of the x86_64 architecture is much worse. I used gcc 4.1.2 on Ubuntu, the simulator is Omnet++. There was already a post about the topic: http://gcc.gnu.org/ml/gcc-help/2006-05/msg00185.html on AMD machines. I could also figure out, that one problem ist the pow() function, maybe there are more functions with poor performance on x86_64 machines. Has anyone an idea about the reasons or how to improve the performance on x86_64 machines? Thanks. Regards, Ralf
