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Will the A11 be 64bit-only

synonys

synonys

macrumors regular
Original poster
Sep 16, 2014
130
139
Given that iOS 11 will drop support for 32bit apps doesn't it make sense for apple to also drop 32bit compatibility in the next SoC? This is possible in the ARM architecture and lack of 32bit compatibility would reduce complexity and free die space for other rumored features.

Ars Technica touched on this a couple of months ago,
"The 64-bit ARM instruction set, also called AArch64, is unique in that it is totally separate from the 32-bit (and ARMv7-compatible) AArch32 instruction set. In the PC world, the x86-64 instruction set is an extension of the 32-bit and 16-bit instruction sets—it was designed that way on purpose, and its easy backward compatibility gave it a decisive advantage over Intel’s 64-bit-only Itanium architecture. As a side effect, it has drawn out the 64-bit transition on PCs for years. Even today, every x86 PC supports 32- and 16-bit code that it will only rarely need to run."

https://arstechnica.com/apple/2017/...-could-mean-for-apples-hardware-and-software/
 
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synonys said:
When we need greater than 16EB of ram.
Click to expand...
I don't get this. If 64 bit just means it can have more than just 4GB of ram, why are there 32 bit and 64 bit software versions? Why can't 32 bit systems use 64 bit programs and why can't 64 bit systems use 32 bit programs without including the compatible hardware? Also why does 64 bit software perform better? Every place I go says the only advantage of 64 bit is increased RAM capacity.
 
32 bit processors can use 2^32 or over 4 billion unique addresses, which means that potentially you can have up to 4 GB of memory (2^32 bytes) if you don't use anything else. However, since your processor still needs to have enough free address space to use everything in your device (the graphics memory uses the most as it can easily be 1 GB or more) you are usually limited to just over 3 GB of ram on average for 32 bit processors. Imagine a giant map, and how everything connected to your device needs to be on the map.

Aside from being able to use 4 GB and more of ram, 64 bit processors are faster as they do all their work in 64 bit sized chunks (hence the name). While it won't be twice as fast as 32 bit processors, they are enough of an improvement that everyone is struggling to convert to 64 bit software for the performance benefits. Why Apple insists that every simple 32 bit app will slow everything down is another matter. Perhaps they plan to make devices 64 bit only, so this is their excuse as to why the apps people bought will eventually become worthless.

32 bit processors cannot easily run 64 bit apps as the app cannot suddenly redesign itself to fit inside a 32 bit processor. It is much easier (and smaller) to have both 32 bit and 64 bit versions over having a massive app that will have twice as much code as needed (and consider that you will waste space due to never using half of the app). There might be a way to run 64 bit on 32 bit, but imagining how much work you would need to do it is likely cheaper to transition to newer hardware.

64 bit processors have part of their chip dedicated to running 32 bit apps on a 64 bit processor, which is why it can use both. It is also much easier to convert 32 bits into 64 bits, which is why most 32 bit apps will run on a 64 bit processor.

As to when 128 bits will happen? Maybe when we will need 2^64 (16 EB or 16 billion GB) of addresses.
 
maxjohnson2 said:
I updated to iOS 11 beta and it doesn't work with 32bit apps, so yes, only 64bit moving forward.
Click to expand...

We are not talking about software or the OS. We're speculating about whether the physical chip in the next iPhone will drop 32bit support all together.

Since iOS 11 will not support 32bit it makes sense for apple to remove the 32bit parts of their chips going forward.
 
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