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The IA-32 Execution Layer (IA-32 EL) is a software emulator in the form of a software driver that improves performance of 32-bit applications running on 64-bit Intel Itanium-based systems, particularly those running Linux and Windows Server 2003 (it is included in Windows Server 2003 SP1 and later and in most Linux distributions for Itanium). The IA-32 EL bypasses the slow x86 hardware emulation which is available on pre-Montecito Itanium models.

The IA-32 EL used a two-phase (later three-phase) approach: initially it quickly translated every piece of code at a basic block level, adding certain instrumentation for detecting hot code; then hot code was dynamically optimized at a super-block level, and the optimized translated code replaced cold code on the fly. Later interpretation engine was added that allowed to avoid altogether translation of code executed just a few times - cold non-optimized translation became thus the second phase, and hot optimized translation became the third phase. IA-32 Execution Layer supported self-modifying code, and could even optimize it quite well.

Part of the software is under the LGPL and part is under an Intel proprietary license.

See also

• Itanium
• List of Intel Itanium microprocessors

References

1. The IA-32 Execution Layer 4.3 Software Driver (microsoft.com)
2. "IA-32 Execution Layer: Technical Whitepaper". Intel.
3. "Intel Software Development Products". Intel. Archived from the original on April 23, 2007.

External links

• Intel® Itanium® Processor Family Reference Guide: IA-32 Execution Layer

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