Intel could have beaten AMD to 64-bit transition but wrongly chose not to, engineers reveal

The large picture: The x86-64 instruction group was initially announced by AMD successful 1999, providing a important upgrade to nan starring PC computing architecture. The exertion proved highly successful, and Intel had to pursuit aft a competitor for nan first clip successful x86 history. Things could person been overmuch different, though.

Intel had a solution fresh to adhd 64-bit features to nan "classic" 32-bit x86 ISA, but nan institution chose to push guardant pinch nan Itanium cognition instead. A caller snippet of exertion history has precocious emerged from a year-old Quora discussion. Intel's erstwhile "chief x86 architect," Bob Colwell, provides a fascinating tidbit of antecedently chartless information.

AMD technologist Phil Park was researching nan history down nan x86-64 transition, erstwhile he discovered nan conversation. Colwell revealed that Intel had an inactive soul type of nan x86-64 ISA embedded successful Pentium 4 chips. The company's guidance forced nan engineering squad to "fuse off" nan features.

The functionality was there, but users could not entree it. Intel decided to attraction connected nan 64-bit autochthonal architecture developed for Itanium alternatively of x86-64. The institution felt that a 64-bit Pentium 4 would person damaged Itanium's chances to triumph nan PC market. Management allegedly told Colwell "not once, but twice" to extremity going connected astir 64-bits connected x86 if he wanted to support his job.

The technologist decided to compromise, leaving nan logic gates related to x86-64 features "hidden" successful nan hardware design. Colwell stake that Intel would request to pursuit aft AMD and quickly instrumentality its type of nan x86-64 ISA, and he was right. Itanium CPUs had nary autochthonal backward compatibility pinch 16-bit and 32-bit x86 software, truthful nan architecture was 1 of nan worst commercialized (and technology) failures successful Intel's history.

Also see: The Rise, Fall and Renaissance of AMD

The x86-64 ISA was afloat compatible pinch "legacy" x86 codification while introducing a caller 64-bit mode pinch much powerful instructions, larger vector registers, and more. It besides provided nan expertise to usage vastly larger virtual and beingness representation pools compared to 32-bit CPUs. AMD first implemented nan x86-64 instruction group pinch K8-based Athlon 64 and Opteron chips, which yet forced Intel to "go 64-bit" pinch a modified type of nan NetBurst architecture (Pentium 4).

Bob Colwell made important contributions to Intel's history, managing nan improvement of celebrated PC CPUs specified arsenic Pentium Pro, Pentium II, Pentium III, and Pentium 4 earlier retiring successful 2000. Meanwhile, today's x86 chips marketed by Intel and AMD still clasp afloat backward hardware compatibility pinch astir each programme developed for nan x86 architecture.