[cd2013]

To be precise:

https://stackoverflow.com/a/8869596
https://en.wikipedia.org/wiki/Physic...ress_Extension

Yes, a 32-bit architecture is limited to addressing a maximum of 4 gigabytes of memory. Depending on the operating system, this number can be cut down even further due to reserved address space.

This limitation can be removed on certain 32-bit architectures via the use of PAE (Physical Address Extension), but it must be supported by the processor. PAE eanbles the processor to access more than 4 GB of memory, but it does not change the amount of virtual address space available to a single process—each process would still be limited to a maximum of 4 GB of address space.