Itanium’s Rise and Fall: Intel’s 64‑Bit Gamble vs AMD64 Evolution

32‑bit CPUs could address only about 4 GB of memory, limiting high‑end workstations and servers. Intel dominated the PC market but lacked a presence in the UNIX workstation space, where RISC chips such as SPARC, PA‑RISC, and Alpha ruled. To break into that segment, Intel launched a multi‑billion‑dollar effort to create a 64‑bit successor to x86.

Extending x86 vs. a Clean Sheet

Intel feared that extending the legacy CISC x86 architecture would inherit decades of baggage and make future innovation impossible. The company also worried that AMD and other cloners could eventually control the x86 standard. A clean‑sheet design promised total control over the architecture and a chance to escape legacy constraints.

VLIW and EPIC Explained

VLIW (Very Long Instruction Word) aims to maximize instruction‑level parallelism by moving scheduling from hardware to the compiler. The compiler must predict program flow; when predictions fail, compensation code is required, adding complexity. Historically, VLIW proved difficult because compiler technology struggled to generate optimal schedules. EPIC (Explicitly Parallel Instruction Computing) is the implementation of VLIW in Intel’s IA‑64 instruction set.

Intel‑HP Alliance and the Merced Chip

In 1994 HP sought a manufacturing partner with scale, while Intel needed a 64‑bit architecture. The two companies partnered to turn HP’s PA‑Wide Word (PA‑WW) concept into a successor for x86. Intel’s internal “bake‑off” between its own 64‑bit effort and PA‑WW resulted in PA‑WW winning, evolving into EPIC and the IA‑64 instruction set. The first IA‑64 chip, codenamed “Merced,” carried the commercial brand name Itanium.

Execution Challenges and Internal Conflict

Cultural clashes erupted between HP’s consensus‑based management and Intel’s “constructive confrontation” style. Design complexity forced multiple delays from 1998 to 2000, and the chip was eventually forced onto a 180 nm process to fit on a single die. Meanwhile, the Pentium Pro (P6) team in Oregon demonstrated that 32‑bit x86 still held significant performance potential, fueling rivalry with the Santa Clara team developing Merced.

AMD’s Evolutionary AMD64 Path

Intel excluded AMD from IA‑64 licensing, prompting AMD to pursue an evolutionary route: extending x86 to 64 bits (AMD64/x86‑64). AMD64 offered full backward compatibility, which developers and users preferred over the radical IA‑64 shift. Jim Keller authored the AMD64 specification, and Atiq Raza pushed the extension forward, allowing AMD to capture the high‑end market without abandoning the existing software ecosystem.

Rise of Commodity Compute Clusters

The industry gravitated toward compute clusters built from cheap, commodity x86 servers running Linux. This horizontal scaling model favored cost efficiency and resilience over the high‑performance, proprietary mainframe approach embodied by Itanium. Intel’s own Xeon line became Itanium’s biggest competitor as customers migrated to cluster architectures.

Market Reality and Legacy

Analysts once projected $14 billion in Itanium sales by mid‑2004, yet actual sales reached only about $600 million. Intel invested roughly $5 billion in the project, and HP bought 85 % of Itanium production, later paying Intel $690 million to keep the line alive until 2017. The final Itanium chip (Kittson) shipped in 2021, marking the end of a chapter that some still consider unfinished.