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

Mon Dec 8 06:06:16 UTC 2008
Kenneth Burgener <kenneth at mail1.ttak.org>

I am curious what should be the benchmark for making the choice of 
switching from 32bit to 64bit Linux?  I have a few assumptions below. 
Is my logic sound?  (This is a follow up to the "Adding RAM" thread)


1.  4GB Memory.  The main benefit of 64bit mode is the ability to 
address more than 4GB of RAM.  I assume that you use 64bit mode if you 
want to *efficiently* have more than 4GB of RAM, or intend to upgrade 
past 4GB in the foreseeable future.  (I emphasize "efficiently" because 
PAE is an option, if you are desperate to keep 32bit mode with more RAM)

2.  Overhead.  It is my assumption that 64bit has more "overhead", being 
that the registers are now 64bits long, instead of 32bit, which would 
mean more bits to pass around the system.  So if you have less than 4GB 
of RAM, 32bit mode would perform better than 64bit mode.

3.  Compatibility.  Linux has made incredible strides to make 64bit 
Linux very robust and compatible, but I still occasionally see binary 
applications/plugins/drivers that popup which are 32bit mode only.  This 
is usually only a problem with Desktop systems that want bleeding edge, 
or not as well supported software.

4.  Desktop vs Servers.  Current "desktops" machines generally have 
around 2GB of RAM, or less.  Current "server" machines generally have 
around 2GB of RAM, or more (much more).  Because of the overhead (#2) 
and compatibility (#3) I would think that Desktops would benefit from 
using 32bit mode, and Servers would benefit from 64bit mode.

Is my logic sound?