There are some inaccuracies in the text. The truth is, AMD could not copy Intel's 64 bit architecture. Intel created a separate company to circumvent licensing

There are some inaccuracies in the text. The truth is, AMD could not copy Intel's 64 bit architecture. Intel created a separate company to circumvent licensing agreement which grants AMD access to 86 instruction set. Next, amd64 is not compatible with ia32. BUT it enables run both ia32 and amd64 code almost seamlessly AND with no major performance impact. Note that ia64 does allow to run ia32 but with notable performance hit (justifiable by commercial interests only).