The total memory (RAM) that can be added to a computer depends on the size of the address registers built into the CPU. For example, most 32-bit CPUs have a 32-bit address register that can access 4GB (four gigabytes) of memory.
The maximum memory capacity in a 64-bit computer is essentially limitless (see chart below) because a 64-bit address register can access 16 exabytes of memory. See
address register,
flat address space and
memory.
Simultaneous
Maximum Bytes
CPU Memory Processed
8-bit 65KB 1
16-bit 1MB 2
32-bit 4GB 4
64-bit 16EB** 8
** Limitless for all intents
and purposes. No computer
contains that much RAM.
See binary values.