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.)

Cheers,

_______________________________________
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: [email protected]

On 5/14/2014 11:05 AM, Nathaniel Echols wrote:

On Wed, May 14, 2014 at 1:44 AM, Matteo Colombo <[email protected]> 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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