The instruction decoders on x86 processors consume a lot of silicon. x86's instruction retirement also imposes additional overhead due to book-keeping on the scheduler. Eliminating the x87 stack-based FPU is been a gradual process involving an evolving SIMD instruction set that started as a hack.
In reality, resources trumps ISA. x86 has the advantage of hand-optimized logic combined with the best high-performance VLSI manufacturing in the industry.
In spite of that, Itanium blows the doors off of every x86 processor built on the same fabrication technology -- notice that so far, the Itanium and x86 contemporaries are built on fab processes that have been two generations apart, with the high-volume part using the newest process.
The instruction decoders on x86 processors consume a lot of silicon. x86's instruction retirement also imposes additional overhead due to book-keeping on the scheduler. Eliminating the x87 stack-based FPU is been a gradual process involving an evolving SIMD instruction set that started as a hack.
In reality, resources trumps ISA. x86 has the advantage of hand-optimized logic combined with the best high-performance VLSI manufacturing in the industry.
In spite of that, Itanium blows the doors off of every x86 processor built on the same fabrication technology -- notice that so far, the Itanium and x86 contemporaries are built on fab processes that have been two generations apart, with the high-volume part using the newest process.