Do you need a 64-bit phone?

Someone once said that whenever a question is posed in a headline, the answer is always no. This isn't always true and the situation with 64-bit processors in mobile phones is actually more complicated than a simple no, or yes for that matter. There is no doubt that one day you will need a 64-bit processor in your smartphone, but not today.

The question of whether you need a 64-bit processor has only just arisen because of Apple's launch of the iPhone 5S, which sports a new A7 processor with 64-bit architecture. It runs a 6-bit OS, has 64-bit drivers and so on. But what difference does it make and is 64-bits twice as good as 32-bits?

PCs and Apple Macs, Windows and OS X - everything is 64-bit these days and the reason is that there are limits on the amount of memory that processors can access. A 16-bit processor can access 2^16 memory locations, a 32-bit processor can access 2^32 memory locations and a 64-bit processor can access 2^64 (that's 2 multiplied by itself 64 times - 2x2x2x2x...).

Let's put this in terms that are easy to understand. A 32-bit processor can access a maximum of 4Gb of memory. That is why desktop and laptop computers and the operating systems they run are all 64-bit these days. If they weren't we would never be able to use more than 4GB of memory. (In practice even 4GB isn't accessible by some memory locations are reserved for system use.)

If you want to put 8GB of RAM in your PC or Mac, that's fine now, but a few years ago it wasn't possible. I have 4GB in the Mac I'm using right now, but it sometimes struggles and it could really do with more. The reason is that apps and operating systems grow in size as more features are added.

Mobile phones and tablets are not yet struggling for memory in the same way. Budget models only have 1GB of memory, premium models have 2GB, and 3GB of RAM in a phone or tablet is rare. There is still room for apps and mobile operating systems to grow and right now a 32-bit processor can address all the memory they need.

As apps and mobile operating systems grow there will come a day when 4GB just isn't enough and then we will need a 64-bit processor so that phones can have 6GB, 8GB or more of RAM. That day is a long way off though.

In addition to providing access to more memory, a 64-bit processor can access data in 64-bit chunks. If it needs to access a lot of data it can do so more efficiently and this means that some apps will run faster, but they do have to be designed for 64-bit processing. Accessing small amounts of data can be slower because it's less than the optimum 64-bit chunk. Apps designed for 32-bit processors, which is pretty much all of them right now, might even run more slowly on a 64-bit processor.

As far as performance goes, there will be gains and losses. Some apps will be faster, but others might be slower on a 64-bit chip. Overall though, there are usually more benefits.

Don't fall into the trap of thinking that 64-bits is necessarily better than 32-bits, or getting into a "My phone is better than your phone because it's 64-bit," argument. The main advantage of the A7 in Apple's iPhone 5S is that it's fast.