[phenixbb] fem command/memory error

Roger Rowlett rrowlett at colgate.edu
Wed May 14 08:13:15 PDT 2014

4 Gb is the limit of addressable memory for 32-bit machines. The amount 
of usable memory (RAM) is anywhere from around 2-3 Gbyte depending on 
hardware configuration. Some hardware (e.g., a graphics card) reserves 
memory space for itself, decreasing the amount available for usable RAM.

I believe all relatively modern (last 5-10 years?) CPUs are 64-bit 
capable. A 64-bit machine should be able to address 16 Gbyte of memory. 
(Minus hardware deductions for usuable memory space.)


Roger S. Rowlett
Gordon & Dorothy Kline Professor
Department of Chemistry
Colgate University
13 Oak Drive
Hamilton, NY 13346

tel: (315)-228-7245
ofc: (315)-228-7395
fax: (315)-228-7935
email: rrowlett at colgate.edu

On 5/14/2014 11:05 AM, Nathaniel Echols wrote:
> On Wed, May 14, 2014 at 1:44 AM, Matteo Colombo 
> <Matteo-Maria.Colombo at ibs.fr <mailto:Matteo-Maria.Colombo at ibs.fr>> wrote:
>     My OS is Ubuntu precise 12.04 LTS, system 32 bit
> One note of caution: if you are running a 32-bit architecture or OS, 
> upgrading the memory may not help, because it will be limited in how 
> much it can address at once.  (I forget if the limit is 2GB or 4GB; it 
> may be OS-dependent.)  At this point I would recommend using 64-bit 
> for everything if possible, and especially not purchasing any systems 
> that are 32-bit only.  (Are these even sold any more?)
> -Nat
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