IA-64 Itanium (not to be confused with x86-64 / AMD64) is a family of 64-bit Intel microprocessors based on VLIW with explicit instruction-level parallelism, in which the compiler decides which instructions to execute in parallel. This contrasts with traditional superscalar architectures, which depend on the processor to manage all instruction dependencies at runtime. It is unrelated to x86-64.
Itanium (/aɪˈteɪniəm/) is a family of 64-bit Intel microprocessors that implement the Intel Itanium architecture (formerly called IA-64). Intel markets the processors for enterprise servers and high-performance computing systems. The architecture originated at Hewlett-Packard (HP), and was later jointly developed by HP and Intel.
The Itanium architecture is based on explicit instruction-level parallelism, in which the compiler decides which instructions to execute in parallel. This contrasts with traditional superscalar architectures like x86 or ARM, which depend on the processor to manage instruction dependencies at runtime (to give the illusion of each instruction running in program order).
Itanium cores up to and including Tukwila execute up to six instructions per clock cycle.
http://en.wikipedia.org/wiki/Itanium
Itanium's EPIC (Explicitly Parallel Instruction Computing) is based on VLIW. The instruction format is a 128-bit VLIW bundle of 3x 41-bit instructions, and a 5-bit template which encodes instruction types, and "stops" which mark data dependencies between groups of VLIW bundles.
IA-64 is completely unrelated to x86-64 / AMD64, x86, or IA-32 (32-bit x86). The same company (Intel) was behind both IA-64 and IA-32, but the ISAs are completely different, IA-64 being a VLIW and x86-64 being a CISC with variable-length instructions and a small number of architectural registers.
Early Itanium hardware had hardware support for executing IA-32 instructions to ease adoption by the target market (people already using x86), and the manuals define which IA-64 registers are used for IA-32 state. It was later dropped in favour of software emulation.
- Intel® Itanium® Architecture Software Developer's Manual (all 4 volumes): https://www.intel.com/content/www/us/en/processors/itanium/itanium-architecture-vol-1-2-3-4-reference-set-manual.html assembly language / ISA manual.
