Intel C2D COREs not used equally in FreeBSD 7.0-CURRENT i386
des at des.no
Wed Jun 6 10:47:58 UTC 2007
Oliver Fromme <olli at lurza.secnetix.de> writes:
> It's a common mistake to assume that amd64 only makes sense
> if you have >= 4GB RAM. There are several reasons why it
> might be useful to switch from i386 to amd64:
> - Most programs (though not all) will run faster, because
> in amd64 mode there are twice as many general-purpose
> registers, giving compilers much better opportunities
> for optimizations and caching of values, and reducing
> slow memory accesses.
"twice as many" is an understatement. AMD64 has 16 GPRs vs i386's 8 if
you consider BP, SI, DI and SP as GPRs (as the AMD and Intel literature
does); in practical terms the score is 12 to 4.
> - Some applications might benefit from a larger virtual
> address space > 4 GB. (Note that this is not related
> to the amount of physical RAM!)
For instance, Varnish maps its entire storage into memory, and will
benefit greatly from the increased address space.
> In practice there's (almost) only one reason not to run
> FreeBSD/amd64 on amd64-capable hardware: If you depend
> on a certain piece of software which is known not to run
> correctly in 64bit mode. Fortunately those are not many.
The only one I can think of (for a desktop) is the Flash plugin.
Dag-Erling Smørgrav - des at des.no
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