The massive image: The x86-64 instruction set was initially introduced by AMD in 1999, offering a big improve to the main PC computing structure. The expertise proved extremely profitable, and Intel needed to chase after a competitor for the primary time in x86 historical past. Issues may have been a lot completely different, although.
Intel had an answer prepared so as to add 64-bit options to the “basic” 32-bit x86 ISA, however the firm selected to push ahead with the Itanium operation as an alternative. A brand new snippet of expertise historical past has just lately emerged from a year-old Quora dialogue. Intel’s former “chief x86 architect,” Bob Colwell, offers an interesting tidbit of beforehand unknown data.
AMD engineer Phil Park was researching the historical past behind the x86-64 transition, when he found the dialog. Colwell revealed that Intel had an inactive inner model of the x86-64 ISA embedded in Pentium 4 chips. The corporate’s administration compelled the engineering crew to “fuse off” the options.
The performance was there, however customers couldn’t entry it. Intel determined to deal with the 64-bit native structure developed for Itanium as an alternative of x86-64. The corporate felt {that a} 64-bit Pentium 4 would have broken Itanium’s possibilities to win the PC market. Administration allegedly informed Colwell “not as soon as, however twice” to cease occurring about 64-bits on x86 if he needed to maintain his job.
The engineer determined to compromise, leaving the logic gates associated to x86-64 options “hidden” within the {hardware} design. Colwell guess that Intel would wish to chase after AMD and rapidly implement its model of the x86-64 ISA, and he was proper. Itanium CPUs had no native backward compatibility with 16-bit and 32-bit x86 software program, so the structure was one of many worst industrial (and expertise) failures in Intel’s historical past.
Additionally see: The Rise, Fall and Renaissance of AMD
The x86-64 ISA was absolutely appropriate with “legacy” x86 code whereas introducing a brand new 64-bit mode with extra highly effective directions, bigger vector registers, and extra. It additionally supplied the flexibility to make use of vastly bigger digital and bodily reminiscence swimming pools in comparison with 32-bit CPUs. AMD first carried out the x86-64 instruction set with K8-based Athlon 64 and Opteron chips, which in the end compelled Intel to “go 64-bit” with a modified model of the NetBurst structure (Pentium 4).
Bob Colwell made important contributions to Intel’s historical past, managing the event of well-liked PC CPUs akin to Pentium Professional, Pentium II, Pentium III, and Pentium 4 earlier than retiring in 2000. In the meantime, in the present day’s x86 chips marketed by Intel and AMD nonetheless retain full backward {hardware} compatibility with almost each program developed for the x86 structure.
