>> my question is if you use m32 flag, is there a limitation of the ram that you can use
Since the address space becomes 32 bit the maximum memory a 32 bit process can possible address is 4GB. That said, in reality the amount of user memory is a lot less (usually 1 or 2 GB) since the rest is reserve in the processes memory map for various other reasons (such as for use my the kernel to map devices - this is probably a poor example).
