|If you think Intel would eat its own shoes before it adopted AMD64, guess again, it will be compatible with AMD64. If you doubt this, think about one thing, why this is happening. It is not Intel's doing, not by a long shot. While it may use a different name, like the old x86-64, or even Extended x86, it will run all the software that AMD does. Mmmmm, shoes are tasty.
So, why is this again? Simple, MS. Microsoft will not support a different 64 bit platform, and frankly I don't blame it, it costs a lot of money to do that. MS gave Intel the choice, support AMD's instruction set, or do without Windows. MS won that battle pretty handily.
I'm not really 100% sure about this. Microsoft has indeed a very high marketshare, so it would be very very bad for Intel if they would not make a 64bit version of Windows for Intel.
But on the other side Intel also has a very big marketshare in the desktop market of around 80%, and AMD only around 15%. So not supporting Intel his 64bit extension would be a very bad move for Microsoft.
Source : The Inquirer