IA-64 vs. AMD64

Itanium is a family of 64 bit Intel microprocessors. It was designed with the purpose of implementing Intel Itanium architecture. This is what encapsulates IA-64. More specifically, these microprocessors are marketed for particular use in enterprise servers, and high performance computing systems. It was a structure that was created by Hewlett-Packard (also known as HP) and then merged into a collaboration between HP and Intel.

AMD64 is an instruction set that was implemented by AMD’s Athlon 64, Athlon 64 FX, Athlon 64 X2, Athlon X2, Opteron, Phenom, Phenom II, Turion 64, Turion 64 X2, and Sempron processors. It was created as a direct alternative to the Intel and HP IA-64. It was initially designed as an evolutionary way to implement 64 bit computing capabilities into the x86 architecture, which was already in existence.

Intel’s approach had been to create an entirely new 64 bit architecture when they conceived IA-64. It was mostly a way in which Intel attempted to advance the performance of the 64 bit microprocessors beyond the designs that were already on the market. Itanium was a drastic departure from the legacy x86 and architectures of the same foundation. It is based explicitly on instruction level parallelism – this is when the compiler makes the decisions about which instructions should be executed in parallel. This was in direct contest with those architectures that were built to depend on elaborate processor circuitry, in order to keep track of the instruction dependencies during runtime.

Some of the architectural features of the AMD64 that separates it so drastically from the IA-64 architecture are 64 bit integer capability (in which the general purpose registers, or GPRs, expand from 32 bits to 64 bits, allowing all arithmetic and logical operations to function in the 64 bit environment), additional registers (which increased from eight to 16, in order to keep more local variables in registers rather than on the stack), additional XMM registers, larger virtual address space, larger physical address space, instruction pointer relative data access, SSE instructions, No Execute bit, and removal of older features. AMD64 also functions in both long mode (which is the combination of the processor’s native 64 bit mode and a combined 32 bit and 16 bit compatibility mode) and legacy mode (which is the mode used by 16 bit and 32 bit operating systems – in which the processor acts as an x86 processor).

Summary:

1. IA-64 is an Intel Itanium architecture that is used in enterprise servers and high performance computing systems; AMD64 is an instruction set in direct contest of the IA-64 architecture.

2. IA-64 is based on explicit instruction level parallelism; AMD64 functions both in long mode and in legacy mode.

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