Athlon64 processors can run both 32-bit and 64-bit applications, but over 90% of current software is still 32-bit, limiting optimization opportunities. The discussion suggests that optimization for Athlon64 largely depends on software developers transitioning to 64-bit compilers. There is speculation about the availability of a 64-bit version of Longhorn, with expectations that it will be released when the operating system reaches the market. For those with access to application source code, compiling with GCC's amd64 option is recommended for leveraging 64-bit capabilities. Additionally, there are specialized 64-bit operating systems available for AMD 64, such as those from SuSE, which can help users fully utilize 64-bit technology.
