iPhone Why Go 64bit?

[C DM]

You meant the other way around? 😉 All 2/3GB Android devices are 32-bit only.

Generally: look at the Safari / UIWebView memory usage on the 64-bit devices. It was very memory-hungry on 32-bit ones; on 64 bits, it's even worse.

Ah, now I see what you were trying to say by your earlier statement. So 64-bit architecture/applications noticeably increases the memory needs/usage?

 

[Menneisyys2]

Ah, now I see what you were trying to say by your earlier statement. So 64-bit architecture/applications noticeably increases the memory needs/usage?

Noticeably, depending on the app / content - see the dedicated reports.

 

[Infinus.gold]

I'm curious as to why apple would change the 5S over to a completely 64bit architecture and then only include 1 gig of RAM. Why would they do that? Is there any performance benefit? Thoughts?

64bit will provide wide registers,

Many of the instructions can be processed in one cycle,
Wide registers will provide bigger data storage & processing capability,
Large array of peripherals can be connected and access simultaneously
Better security can implemented as broader bandwidth of CPU registers & internal memory.

Why do you need more than 1 GB RAM ?

more RAM--> more battery needed to hold charge --> battery deplete faster

Why to buy something if you don't need one....

SamS**g and other has to rely on other for hardware design (e.g., Qualcomm)... they really don't optimize software and hardware well enough to make a perfect blend.... and result is large memory needed to process same thing that can be optimized and done...

hope this make things clear...

 

[deluxeshredder]

I'm curious as to why apple would change the 5S over to a completely 64bit architecture and then only include 1 gig of RAM. Why would they do that? Is there any performance benefit? Thoughts?

Marketing.

One day, "the new iOS" will run badly on 1GB of RAM, so 5S owners will rush to buy "the new iPhone".

Why do you need more than 1 GB RAM ?

more RAM--> more battery needed to hold charge --> battery deplete faster

RAM doesn't consume much energy. In fact, extra RAM can increase battery life because it can reduce memory swapping which is far more power-hungry.

 

[Menneisyys2]

Why do you need more than 1 GB RAM ?

more RAM--> more battery needed to hold charge --> battery deplete faster

Typical Apple "explanation". The truth is that the increase in memory size contributes to increased power use only a little bit and a LOT less than even the lowest backlight usage. I'd say you'd notice a 1% difference (at most!) in battery life with a 2GB iPhone 5s.

And yes, I know quite a little bit about hardware. I've been using touchscreen mobile devices since the original Newton and mobile, programmable devices since the PC1500 back in 1981.

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RAM doesn't consume much energy.

Indeed.

In fact, extra RAM can increase battery life because it can reduce memory swapping which is far more power-hungry.

Yup, but this doesn't apply to iOS as it has no virtual memory / swapping. (Apart from some JB hacks doing this back in around 2008-2009.)

 

[Krevnik]

Yup, but this doesn't apply to iOS as it has no virtual memory / swapping. (Apart from some JB hacks doing this back in around 2008-2009.)

It does have virtual memory, just no swap file. The distinction is kinda important.

Virtual memory does more than just offer up the ability to swap pages out to disk. Virtual memory is how you isolate processes, and memory map files. The memory mapped file never gets loaded into RAM until you try to read from it, where the kernel will copy the page into RAM at that point.

iOS will jettison non-dirty pages to make room in RAM as needed. Code pages are a prime target for this. Another good target is a memory mapped file that is only used to read. Also, if the app allocates a chunk of memory, but never writes to it, then those pages are free to be jettisoned as well to make room in RAM without affecting the state of the program.

And when you do need these pages that get jettisoned, it is more expensive to page back in, as you may have to read in from flash (or zero it out if the page originally belonged to a different process), and possibly jettison MORE pages in order to make room for this new one.

So the only real cost that is avoided is the cost of writing pages to disk for swapping. You still incur the very real cost of swapping pages back into RAM.