There are major architectural differences between Intel and AMD's 64-bit machines.
The primary difference between the two chips is that Intel's Itanium line of processors is a pure 64-bit processor that will only run 64-bit code while AMD's Opteron and Athalon 64 processors are 32-bit/64-bit hybrids. AMD's processors can therefore natively run 32-bit and 64-bit code. The implications of this are huge.
AMD machines have the advantage of running either a 64-bit version of Windows or a 32-bit version, which means that companies can invest in 64-bit hardware today, but don't actually have to make the transition to a 64-bit operating system until they are ready.
The fact that Intel machines can only run 64-bit code doesn't mean that the machines can't run 32-bit applications. The 64-bit version of Windows has a built-in emulator called WOW64 (which stands for Windows 32 On Windows 64). The emulator is completely transparent. You don't have to do anything special to run 32-bit applications.
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About the author: Brien M. Posey, MCSE, is a Microsoft Most Valuable Professional for his work with Windows 2000 Server and IIS. He has served as the chief information officer for a nationwide chain of hospitals and was once in charge of IT security for Fort Knox. As a freelance technical writer, he has written for Microsoft, CNET, ZDNet, TechTarget, MSD2D, Relevant Technologies and other technology companies.
This was first published in March 2007