The 64-Bit Gambit: How AMD Outmaneuvered Intel in the x86-64 Revolution
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"Intel did implement a version of 64-bit x86 in Pentium 4, but it was fused off and no one could use it."
This revelation from Bob Colwell, former Pentium Pro chief architect at Intel, ignited speculation about a pivotal moment in computing history. But newly examined technical reports and insider interviews reveal a more complex story behind the rise of AMD64—a story of corporate strategy, technical hubris, and an industry-defining upset.
The Itanium Bet: Intel's Clean-Slate Gamble
In 1994, Intel partnered with HP on IA64 (Itanium), believing x86's complexity would prevent scaling beyond 32 bits. Dave Cutler, Windows NT architect, noted in Microsoft's 2007 technical report "A History of Modern 64-bit Computing":
"When the IA64 project started it was perceived RISC machines would outstrip CISC... They felt they could get higher performance with VLIW."
Intel's motivations were multifaceted:
- Technical: Belief that x86’s CISC limitations would cap performance
- Business: Creating a patent-protected ISA to escape x86 commoditization
- Strategic: Leveraging HP’s compiler expertise for Explicitly Parallel Instruction Computing (EPIC)
Yet Itanium stumbled: delayed launches, bloated code (20-30% NOPs in early bundles), and poor legacy x86 performance. Meanwhile, AMD spotted an opening.
AMD's Counterstrike: Extending the "Ugly" Architecture
While Intel dismissed x86's future, AMD architect Fred Weber saw opportunity. Rejecting clean-slate ISAs (Alpha, SPARC, even IA64), AMD bet on extending x86 to 64 bits—embracing what Linus Torvalds later called its "charming oddity." Their rationale:
- Market Pragmatism: Developers resisted ISA transitions
- Technical Efficiency: Shared microarchitecture for 32/64-bit modes
- Server Ambitions: "Glueless" SMP designs for scalable systems
Crucially, AMD collaborated openly with Microsoft and Linux communities during AMD64’s development—unlike Intel’s closed IA64 process. Microsoft contributed key features to the spec:
- RIP-relative addressing
- NX bit (critical for security)
- Transparent multicore detection
AMD's collaborative approach with software partners contrasted sharply with Intel's isolationism.
The Unraveling: Market Forces Expose Strategic Fault Lines
By 2003, the market delivered its verdict:
- Itanium: Sold <2,500 servers in its first full quarter
- Opteron: Sold 150,000 units in Year 1, seizing 22.9% server share by 2006
Torvalds’ blunt assessment proved prescient: "IA64 falls flat on its face on code size, price, and real-world performance." Intel scrambled, secretly developing Intel64 (Yamhill/EMT64)—an AMD64 clone—while publicly denying its existence. As revealed in Microsoft’s report:
Intel monitored Windows AMD64 code commits, built internal prototypes, and only disclosed plans to partners in 2002—after AMD shipped silicon.
Prescott Pentium 4 chips with enabled Intel64 shipped in 2004, but the damage was done. Analyst Peter Glaskowsky summarized: "When Intel announced 64-bit x86, Itanium became irrelevant except for the high end."
The Legacy: Why Intel Couldn't "Beat" AMD
Contrary to claims Intel "chose not to" compete in x86-64, evidence shows it was strategically impossible:
1. HP Partnership: Supporting x86-64 would sabotage IA64, violating Intel-HP agreements
2. Internal Conflict: Colwell’s account confirms management ordered 64-bit logic disabled in P4 to protect Itanium
3. Market Realities: Announcing a rival x86-64 ISA would fracture developer support
Intel's Prescott chip eventually adopted AMD64-compatible extensions—a tacit admission of strategic defeat.
The saga underscores a timeless lesson: backward compatibility and ecosystem pragmatism trump architectural purity. As ARM challenges x86 today, AMD’s victory reminds us that silicon alone doesn’t win wars—developers, partners, and timing decide them. Intel’s fused-off transistors symbolize a costly miscalculation: betting against the architecture that now, inefably, runs our world.
Source: Analysis based on "A History of Modern 64-bit Computing" (Microsoft, 2007), insider interviews, and technical reports. Original reporting from Computer Parkitecture.