X86 Emulation on Itanium (IA-32 Execution Layer)
Unlike the modern x86-64 / AMD64 architecture, the Itanium architecture is not capable of executing x86 applications natively due to its completely different architecture design. But since the software support for Itanium was lackluster and migrating from existing x86 systems would be a headache without native software, a compatibility layer had to be provided.
For the first few generations of Itanium, namely until the Montecito line of Itanium 2 CPUs launched in 2006, a hardware emulation layer was built in to all Itanium chips. However it was later discovered that well implemented software emulation of x86 instructions can be faster than the actual hardware emulation, which is why Intel developed and released the IA-32 Execution Layer for Windows and Linux in 2004.
The execution layer was later included in Windows Server 2003 SP1 and later versions of Windows as well as in most Linux distributions released after 2004.
