If you think that having a 64bit cpu in the iPhone 5s is a waste because you need more than 4gb of memory to take advantage, you’re wrong. It’s not just about how much it can access but about how and when. Here’s the best explanation on the net I’ve found to explain What the iPhone 5s ’64-bit’ processor means, in plain English.
Apple has just announced the release of the iPhone 5s and jaws hit the floor when Apple also dropped in that it’s the first phone to include a 64-bit processor.
“Great! What does that mean for me?” You ask. Well we’re here to explain.
In the shortest of paragraphs, a 64-bit A7 processor means the iPhone just got a whole lot more powerful. Theoretically double the power and speed, but in reality, it’s probably a 15-30% speed increase. Certain apps written for the 64 bit iPhone (not many at the moment) can make better use of CPU and RAM. High-end games are a prime example.
Ok now explain the science in plain English:
(I can’t take credit for this explanation but it’s one I remembered reading in a comment on Reddit about a year ago which helped get my head around it. I’ve altered it for the purposes of explaining the iPhone 5s’ 64-bit processor.)
“Think of the iPhone as a great library. There are all kinds of books (storage) but also a librarian who helps figure out what books you need. The librarian has 32 assistants who help fetch books on bicycles and bring them back to the librarian. If someone comes in wanting all the books on dinosaurs, and there are 65 of such books, the books will all get there in three trips. The first trip all the assistants go out and get the books on dinosaurs, then go back and on the second trip they all get another book and on the third trip only one has to go and get data, but it still takes just as long, since the important thing is how long a trip takes.
So to get the books it requires three bicycle trips (but we can just call them cycles, so three cycles). However, if the librarian had 64 assistants, it would only take two cycles. There would be a dramatic speed boost, but NOT double, since there would still be one trip where only one assistant was needed, while the others are there but unable to make it go faster.
If there were 256 books on dinosaurs, then with 32 assistants it would take 8 cycles but with 64 the process would only take 4.
An iPhone works in much the same way. The iPhone fetches data from memory, but can only fetch so much at one time. An iPhone running at 32 bits can only handle 32 bits of data during a clock cycle. A 64-bit iPhone can fetch 64 bits of data (and work on it) during one clock cycle which means improved speed, power and efficiency.”
So there you have it. It’s more efficient and although not technically faster speed wise it can pull more data over one cycle.