wordpress memory

hi all. i confused on what the problem may be with my memory, not sure where to start. I’ve done google but not sure if i’m looking for php help mysql help or wordpress help, or all three.

I have a dedicated server starting with 512k memeory.
the server is centos 6 with nginx (not apache).

when i start nginx and mysqld there is no real memory change ( about 5% of ram used).

but when i install wordpress the memory exploades to 125%. so high i had to upgrade my server to 1g of ram, which the memory now sits at 60%.

this is too high. I want to run it on the original 512 but i don’t know where to start looking for problems.

Can wordpress use that much memory or is it my php.ini? or is it mysql, or all three?

any help to point me in the right direction would be great.
ron g