Summing up the obtained results let me offer you a final diagram showing the performance changes when we switch from Windows XP Professional SP2 to Windows XP Professional x64 Edition in systems based on Athlon 64 with AMD64 support and Pentium 4 with Intel Extended Memory 64 Technology support.
This graph illustrates very clearly that the performance of 32-bit applications in Windows XP Professional x64 Edition is hardly dependent on the type of 64-bit extensions implemented in the CPU. Both: Intel Pentium 4 with EM64T technology and AMD Athlon 64 with AMD64 technology are almost equally efficient when working with 32-bit applications in Windows XP Professional x64 Edition. Note that this efficiency is relatively high in both cases, which slows down the 32-bit applications run in 64bit operating system by maximum 5% in the worst case compared with the performance of the same applications in a 32-bit OS.
When we tested 32-bit applications in Windows XP Professional x64 Edition we obtained pretty logical results. However, let’s now check the performance of Athlon 64 and Pentium 4 processors in native 64-bit programs.