32bit 64bit - how much memory can be accessed by a 32 bit machine?

Question

What is meant by 32bit or 64 bit machine?

It’s the processor architecture…a 32 bit machine can read and write 32bit data at a time same way with 64 bit machine….

whats the maximum memory that a 32 bit machine can access?

It is 2^32=4Gb (4Gigabit = 0.5 GigaByte)

That means 4Gb ram?

If I consider the same way for a 64 bit machine then I can have a ram of 16ExbiBytes ..is that possible?

Are my concepts right?

Answer 1

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.

And yes, theoretically a 64-bit architecture can address 16.8 million terabytes of memory, or 2^64 bytes. But I don't believe the current popular implementations fully support this; for example, the AMD64 architecture can only address up to 1 terabyte of memory. Additionally, your operating system will also place limitations on the amount of supported, addressable memory. Many versions of Windows (particularly versions designed for home or other non-server use) are arbitrarily limited.