[CentOS] Silly question x64 vs i386
John R Pierce
pierce at hogranch.com
Wed Dec 16 21:47:19 UTC 2009
m.roth at 5-cent.us wrote:
> Longer answer: every single move, down at the machine/assembly level, can
> move twice as many bits as on a 32-bit system. That will show up as a very
> serious speed increase in your software.
actually, the pentiums have had a 64bit physical memory bus since the
first 60Mhz version, and all L1/L2 cache <=> physical memory operations
are 64bits. the CPUs have all optimized things like REP MOVSB to move
by 64bit chunks whenever possible.
The main performance advantage of x86_64 vs i686 is in the additional
general purpose registers, this allows the compiler (or assembler
programmer) to minimize the number of load/store instructions to
implement a given sequence of operations.
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