IA-64 is an architecture of Intel itanium. It is used in computing systems of high performance and in enterprise servers. AMD64 happens to be an instruction set that is in a direct contest of IA-64 architecture. IA-64 is just based on level parallelism of explicit instruction; the whole AMD64 performs in both legacy mode and long mode. Few other features of the IA-64 architecture that make it different from the AMD64 architectural design are the integer capability of 64 bit, additional registers, removal of old features, additional XMM registers, bigger physical address space, SSE instructions, bigger virtual address space, no executive bit, and relative data access which points out instruction.
AMD64, on the other hand, functions in such a way that the processor's native 64-bit mode, 16-bit compatibility mode, and a combined 32 bit, which makes the processor act as *86 processor. AMD64 was designed as an alternative to the HP and Intel IA-64.