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.