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> For practical purposes, 64-bit means that the processor in the phone can address more than 4GB of RAM. The 5S has 2GB of ram so it isn’t even taking advantage

by coin 13y ago

> For practical purposes, 64-bit means that the processor in the phone can address more than 4GB of RAM. The 5S has 2GB of ram so it isn’t even taking advantage of it. Interesting observation on the 64-bit processor. From an enduser's point of view, what advantage does a 64-bit CPU have?

jws 13y ago
In this case, twice the registers for less memory bandwidth pressure and a rearchitected instruction set. Some day 64 bit addressing may even be useful.
oakwhiz 13y ago
A 64 bit CPU is possibly faster in terms of integer manipulation. Given a 32 bit CPU and equivalent 64 bit version of the same CPU, with the same pipeline lengths, a 64 bit math operation takes up fewer pipeline stages on the 64 bit CPU (since the operation isn't broken up into 32 bit pieces) which possibly improves things like branch prediction.
- ComputerGuru 13y ago
  ...at the cost of (usually) doubling the amount of memory it takes to store all of your pointers.
corresation 13y ago
It is the naive observation that is far too common. The A7 is about ARMv8, which is an evolutionary step over ARMv7. The 4GB thing is the least relevant aspect of it right now.
- sliverstorm 13y ago
  Apple isn't talking about ARMv8 though, they are talking about 64 bit.
  - corresation 13y ago
    They are talking about improving the processor, and ARMv8 is a (or rather the) 64-bit ARM instruction set. Should Apple have instead talked about registers and wider SIMD, better double floating point, etc? 64-bit is just shorthand for that.
    - derefr 13y ago
      Exactly. We went through this exact same marketing with game consoles, years ago. The N64 was a 64-bit game console! What did that mean? Who cares, it's four times as much as a SNES, and twice as much as a Playstation!
- astrojams 13y ago
  It might be true that the A7 is a significant upgrade, but Apple chose to highlight the 64-bit nature of the chip which to my point isn't too exciting today.
sliverstorm 13y ago
I've heard it suggested that as OSX is now 64bit only, running the iPhone on a 64bit CPU will allow a more unified codebase, which the end user will appreciate in the abstract form of fewer bugs and faster release times.
jobu 13y ago
Aside from marketing, it doesn't appear that 64-bit architecture would have any significant benefit (right now). I haven't seen much other technical information about the A7 core, but it's likely this chip will be used in upcoming iPads, so perhaps there are other significant improvements. Does anyone else know more about this?

by coin 13y ago

jws 13y ago

In this case, twice the registers for less memory bandwidth pressure and a rearchitected instruction set. Some day 64 bit addressing may even be useful.

oakwhiz 13y ago

A 64 bit CPU is possibly faster in terms of integer manipulation. Given a 32 bit CPU and equivalent 64 bit version of the same CPU, with the same pipeline lengths, a 64 bit math operation takes up fewer pipeline stages on the 64 bit CPU (since the operation isn't broken up into 32 bit pieces) which possibly improves things like branch prediction.

ComputerGuru 13y ago
...at the cost of (usually) doubling the amount of memory it takes to store all of your pointers.

corresation 13y ago

It is the naive observation that is far too common. The A7 is about ARMv8, which is an evolutionary step over ARMv7. The 4GB thing is the least relevant aspect of it right now.

sliverstorm 13y ago
Apple isn't talking about ARMv8 though, they are talking about 64 bit.
- corresation 13y ago
  They are talking about improving the processor, and ARMv8 is a (or rather the) 64-bit ARM instruction set. Should Apple have instead talked about registers and wider SIMD, better double floating point, etc? 64-bit is just shorthand for that.
  - derefr 13y ago
    Exactly. We went through this exact same marketing with game consoles, years ago. The N64 was a 64-bit game console! What did that mean? Who cares, it's four times as much as a SNES, and twice as much as a Playstation!
astrojams 13y ago
It might be true that the A7 is a significant upgrade, but Apple chose to highlight the 64-bit nature of the chip which to my point isn't too exciting today.

sliverstorm 13y ago

I've heard it suggested that as OSX is now 64bit only, running the iPhone on a 64bit CPU will allow a more unified codebase, which the end user will appreciate in the abstract form of fewer bugs and faster release times.

jobu 13y ago

Aside from marketing, it doesn't appear that 64-bit architecture would have any significant benefit (right now). I haven't seen much other technical information about the A7 core, but it's likely this chip will be used in upcoming iPads, so perhaps there are other significant improvements. Does anyone else know more about this?