memory usage of code compiled with gcc 3.2

[hektor monteiro x285]

Hi everyone! I am working with an astrophysical code that uses a lot of 
memory (RAM). Basically because of a 3D matrix that I have to define. I 
was working with 1G  of RAM before and could run the code with a cube of 
70^3 cells. Recently I bought a new super machine with 4g of RAM and I 
am using the gcc 3.2 compiler on linux redhat 7.3. But I am not able to 
run more than 70^3 cells on this. Can anyone give me some clue?? I would 
think I should be able to do better no? Is this a linux kernel 
limitation or gcc or something else??

cheers,

Hektor