On 08/17/10 09:43 PM, Joerg Schilling wrote:
"Garrett D'Amore"<garr...@nexenta.com> wrote:
It can be as simple as impact on the cache. 64-bit programs tend to be
bigger, and so they have a worse effect on the i-cache.
Unless your program does something that can inherently benefit from
64-bit registers, or can take advantage of the richer instruction set
that is available to amd64 programs, you probably will see a degradation
when running 64-bit programs.
That said, I think a great number of programs *do* benefit from the
larger registers, and from the richer ISA available to 64-bit programs.
If you have an orthogonal architecture like sparc, a typical 64 bit program is
indeed a bit slower than the same program in 32 bit.
On Amd64, you have twice as many registers in 64 bit mode and this is the
reason for a typical performance gain of ~ 30% for 64 bit applications.
Do you have the data to back that up? Most things I've looked at on X64
are slower in 64 bit mode.
--
Ian.
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