I'm trying to build boost 1.34.1 on mac os X 64-bit. In a previous thread someone(Vladimir Prus) gave the following suggestion: ========================================== You need to pass architecture=x86 address-model=64 in addition to the above to bjam, or you may pass architecture=combined address-model=64 ========================================== and it looks like it was fine with boost 1.36. However when I try with boost 1.34.1 I get the following message: libs/test/src/execution_monitor.cpp:1: error: CPU you selected does not support x86-64 instruction set If I remove the achitecture=x86 option then it compiles, but the resulting libraries are not 64-bit, base on the output from file libbooost-XXX.dylib. Is there anything in the 1.34.1 version preventing me from compiling in 64-bit mode? I'm using gcc 4.0.1. Thanks, Alain