[CentOS] 32bit vs 64bit memory usage
Joshua Baker-LePain
jlb17 at duke.edu
Thu May 21 21:24:12 UTC 2009
On Thu, 21 May 2009 at 4:59pm, Robert Heller wrote
> No, you are not wrong. All x86 flavered 64-bit processors will run as
> 32-bit (i686) processors and when running in 32-bit mode are
> effectively just a i686 as far as any 32-bit program can tell. There
> is no reason NOT to just install a straight 32-bit OS on such a machine
> if there is less than 4gig of virtual memory and non-of the programms
> being run has any reason to use the 64-bit address space. Web hosting
That's not strictly true. On some x86_64 chips, there are extra registers
which are only available when running in 64-bit mode. Running without
those registers can hamper performance, even if the program isn't using
the larger address space. This can make a big difference, e.g., in the
HPC space. Web hosting, yeah, probably not so much. But just saying
"64bit iff >4GB RAM" doesn't tell the whole story.
--
Joshua Baker-LePain
QB3 Shared Cluster Sysadmin
UCSF
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