[CentOS] Is 4GB memory the 64bit switch tipping point?

Ignacio Vazquez-Abrams ivazqueznet at gmail.com
Mon Dec 8 07:02:58 UTC 2008


On Sun, 2008-12-07 at 23:06 -0700, Kenneth Burgener wrote:
> Assumptions:
> 
> 1.  4GB Memory.

> 2.  Overhead.

> 3.  Compatibility.

> 4.  Desktop vs Servers.

> Is my logic sound?

Number 1 is a bit off. But just a bit. Number 2 is solid. Number 3 is...
mostly irrelevant with CentOS. Number 4 is not specific enough.

First, The 4GB limit. Yes, 64-bit allows the OS access to more than 4GB
of *physical* memory. However, it *also* allows (64-bit) processes to
access more than 4GB of *virtual* memory. This can be invaluable in
applications that process a lot of data.

Second, compatibility. Upstream's use of multilib allows 32-bit
applications to be run on a 64-bit system without much trouble. Plugins,
specifically Firefox plugins, have the better part of a solution in the
form of nspluginwrapper. Drivers not much can be done about; fortunately
there aren't too many of those.

Third, desktop versus server. Let's ignore the 4GB limit discussed above
while we examine this one. For PPC versus PPC64 your argument is valid.
For IA-32 versus X86-64, you need to look at what the desktop will be
used for. One of the benefits X86-64 gives you over IA-32 is more
registers within the CPU. Operations involving registers are *much*
faster than operations involving memory, allowing X86-64 apps to be up
to about 15% faster than IA-32 in mathematical, scientific, or
multimedia applications.

-- 
Ignacio Vazquez-Abrams <ivazqueznet at gmail.com>

PLEASE don't CC me; I'm already subscribed
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