The total memory (RAM) that can be added to a computer depends on the address registers built into the CPU. For example, most 32-bit CPUs can address only up to 4 gigabytes (GB) of memory.
The reason the maximum capacity in a 64-bit computer is limitless for all intents and purposes (see chart below) is that 64-bit hardware manipulates (calculates, compares and copies) 64 bits, or 8 bytes, of data at a time. However, the actual memory is addressed with far fewer bits. Look up the number 64 in
binary values, and note that a 64 bit register could address 16 exabytes of memory, which is 16 million terabytes. See
memory.
Bytes
Maximum Processed
CPU Memory Simultaneously
8-bit 65KB 1
16-bit 1MB 2
32-bit 4GB 4
64-bit ** 8
** Limitless for all intents
and purposes. No computer can
be built to accommodate the
64-bit theoretical maximum.
See binary values.