What’s the difference, and will we one day have 128bit systems?
In: Technology
Whether a computer’s 16-bit, 32-bit or 64-bit can refer to a number of different concepts.
– Integer size: How big numbers computers can compute with. 16-bit numbers go up to thousands, 32-bit numbers go up to billions, 64-bit numbers go up to billions of billions. Most problems don’t need bigger than 64-bit numbers. So hardware integer size isn’t likely to go above 64-bit. (For the few problems that *do* need bigger numbers, mostly in pure mathematics and cryptography, you can just write software so it can use as many hardware-based integers as it needs to make an integer of any size.)
– Register width: How many bits a computer can compute with at once. CPU’s have some really wide registers these days (as big as 512 bits). So if you use this definition of “bits,” 512-bit computers are already here. Usually such big registers are *vector registers* meaning they represent a *sequence* of smaller numbers, for example a 512-bit register might represent 32 numbers of 16 bits each.
– Address width: Computers store data in memory. They use a pattern of bits called an *address* to uniquely identify a memory location. Just like a shipping warehouse might use a system of numbered bins, where the first 3 digits represent an aisle, the next digit’s a shelf, and the last 2 digits are a bin on the shelf. This warehouse could handle, at most, a million different products, since the numbering goes from 000000 to 999999. This seems like plenty now, but if the company ever has more than a million products, they’ll need to switch to a new numbering system with more digits. Which is a big job, since not only do the labels on the shelves need to be re-written, but the entire system for running the business will need to be re-done. Computer memory’s pretty similar. Remember the 32-bit number is limited to values in the billions? When computer systems started to have more than a couple billion bytes of memory, they needed a new numbering system for memory, and the OS had to support it. Billions of billions of bytes is a lot of bytes, so we won’t need to switch to 128-bit addresses anytime soon.
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