Understanding of Virtual memory limit for a 32 bit application

Question

Please help me understand this :

If my machine has a Ram (Physical memory) of 2 GB , Will I still have a Virtual address space of 4 GB in a 32 bit machine ?

I have read somewhere that a 32 bit application has a max limit of 2 GB virtual address space. If I have a total of 4 GB VAS , 1 GB is used by OS . So 3 GB is remaining for the applications to use . If I have 2 applications running both using 2 GB of memory ,I want to know if they will work since we are left with only 3GB .Is this where paging comes to picture?

Answer 1

I got the clarification here:

http://social.msdn.microsoft.com/Forums/windowsdesktop/en-US/8d63585e-772d-42e5-a40a-72a9500ac0a7/understanding-on-32-bit-environment-application?forum=windowsgeneraldevelopmentissues#8d63585e-772d-42e5-a40a-72a9500ac0a7

Answer 2

On a 32-bit installation, by default, only 2 GB is made available to processes for their own use. The other 2GB are used by the operating system. On later 32-bit editions of Microsoft Windows it is possible to extend the user-mode virtual address space to 3 GiB while only 1 GiB is left for kernel-mode virtual address space by marking the programs as IMAGE_FILE_LARGE_ADDRESS_AWARE and enabling the /3GB switch in the boot.ini file.

If you wanted to run two applications each with 2GB of memory, you will run into a memory exception when either application tries to use the memory that has already been absorbed but the OS.