quote: There are other benefits over and above the memory addressing aspect
quote: Chandrasekher said 64-bit chips aren't "relevant" in today's smartphones or tablets.
quote: Many have even said that the processor in Apple's new iPhone can't be credited entirely for performance boosts in benchmark tests.
quote: Samsung's Galaxy Note 3 and Note 10.1 2014 have 3GiB of RAM. It's not impossible to expect a 4GiB-or-greater tablet in a year or so.
quote: Qualcomm Executive Dismisses Apple's 64-Bit A7 Chip, Dislikes Google Glass
quote: If you average across all benchmarks theres a 70% performance increase to just recompiling your existing code.
quote: Apple is just the 1st to license it.
quote: be fair now, next year, there will be Android tablets, and possibly phones, with 4GBs of RAM.
quote: Uh, no, it isn't. Remember the Microsoft debacle with 32 bit Windows? Microsoft got caught with its pants down when PC's started shipping with 4 GB of RAM, but due to limitations of 32 bit Windows, could only "see" 3 GB or 3.2 GB or whatever it was.
quote: Physical Memory Map That you have 4GB of RAM does not mean that all physical memory addresses from zero to 4GB actually do reach any RAM. In practice, much of that range of physical address space, most likely at the top, is given over to such things as the system BIOS and devices. You can get some sense of this by starting the Device Manager, opening the View menu and asking to see “Resources by type” or “Resources by connection” and then expanding Memory. What this gives you, however, is at best only an indication. It tells you that some addresses are used for devices. It doesn’t tell you which addresses actually do have RAM (or ROM, for that matter). The memory map that matters most for the question of what physical memory the kernel can use is the map that the loader discovers from the firmware. For machines whose firmware is a PC-compatible BIOS, the means of discovery is int 15h function E820h.3 Unfortunately, the loader does not save this map exactly as learnt from the BIOS, which complicates your inspecting this memory map for yourself. However, Windows Vista introduces some undocumented functions with which a kernel-mode driver can get the map fresh from the BIOS. Such a driver for viewing the firmware memory map is presented separately, along with a small console application that reports the results. You will need administrative privilege to load the driver.Of particular interest once you have the firmware’s memory map for your computer are the ranges that are reported as RAM. This article’s test machine has its 8GB of RAM in four ranges spread through 9GB of address space: The first 3GB of physical address space has RAM in two ranges because some is lost at the top of the first 1MB (for reasons of compatibility that go all the way back to the original IBM PC) and some more is lost at the end of the 3GB. The next 1GB is so much given over to device memory that instead of wasting RAM at 3GB, hardware remaps the RAM from there to the end of all other RAM, where it shows as the last of the ranges. The total amount of addressable RAM in the first 4GB is 3,143,338KB, i.e., 3069MB and 682KB. On this machine, with its present configuration of hardware, if the kernel is limited to the first 4GB as its physical address space, then 3069MB (and the spare change) is all the RAM that the kernel can possibly use. Get the kernel to recognise physical addresses above 4GB, and it picks up the other 5GB, for a total of 8189MB as shown in the picture. If the 4th gigabyte were left at 3GB, Windows would have access only to as much of it as does not get overridden. In practice, RAM might show through in various gaps, so that the amount of RAM accessible below 4GB would be more than 3GB but nowhere near 4GB. If you have exactly 4GB of RAM installed, then getting the kernel to use physical addresses above 4GB will be no benefit to you unless some of your 4GB of RAM is remapped above the 4GB address. Whether this remapping is done at present on your particular machine can be checked by using the separately supplied driver. If it is not done, then whether it can be arranged is an issue of hardware configuration. Check your BIOS Setup, read your chipset manual, or consult your computer’s manufacturer. Of course, for a machine that has exactly 4GB of RAM and has 32-bit Windows Vista pre-installed, you would expect that the manufacturer, having been told by Microsoft that Windows will not see any RAM above 4GB, might not have configured any of the 4GB to be remapped out of sight and into uselessness. You should not be surprised to find that remapping is disabled. Worse, unless the manufacturer anticipates installing other Windows versions on the machine, there is no incentive even to provide for remapping above 4GB as something that you can configure if you want. It may even be that your chipset can’t handle physical memory addresses that are wider than 32 bits. Either way, you don’t have memory above 4GB whatever your operating system. If your chipset does not support remapping, then RAM that is overridden for device memory below 4GB will never be seen as usable RAM by 32-bit Windows even with PAE enabled and is just as much lost to you if you install 64-bit Windows.
quote: It is a marketing gimmick and bragging rights to be the first to 64-bit ARM in a mobile device. Technical people know this but consumers typically don't;
quote: If we compare otherwise-identical 32-bit and 64-bit CPUs, there isn't a whole lot of difference, which is a big part of the confusion around the significance of Apple's move to 64-bit ARM. The move is important, but largely because of specifics of the ARM processor and Apple's use of it.Adding it all together, it's a pretty big win. My casual benchmarking indicates that basic object creation and destruction takes about 380ns on a 5S running in 32-bit mode, while it's only about 200ns when running in 64-bit mode. If any instance of the class has ever had a weak reference and an associated object set, the 32-bit time rises to about 480ns, while the 64-bit time remains around 200ns for any instances that were not themselves the target.In short, the improvements to Apple's runtime make it so that object allocation in 64-bit mode costs only 40-50% of what it does in 32-bit mode. If your app creates and destroys a lot of objects, that's a big deal.ConclusionThe "64-bit" A7 is not just a marketing gimmic, but neither is it an amazing breakthrough that enables a new class of applications. The truth, as happens often, lies in between.The simple fact of moving to 64-bit does little. It makes for slightly faster computations in some cases, somewhat higher memory usage for most programs, and makes certain programming techniques more viable. Overall, it's not hugely significant.The ARM architecture changed a bunch of other things in its transition to 64-bit. An increased number of registers and a revised, streamlined instruction set make for a nice performance gain over 32-bit ARM.Apple took advantage of the transition to make some changes of their own. The biggest change is an inline retain count, which eliminates the need to perform a costly hash table lookup for retain and release operations in the common case. Since those operations are so common in most Objective-C code, this is a big win. Per-object resource cleanup flags make object deallocation quite a bit faster in certain cases. All in all, the cost of creating and destroying an object is roughly cut in half. Tagged pointers also make for a nice performance win as well as reduced memory use.ARM64 is a welcome addition to Apple's hardware. We all knew it would happen eventually, but few expected it this soon. It's here now, and it's great.
quote: With the exception of Apple and Motorola, literally every single OEM we’ve worked with ships (or has shipped) at least one device that runs this silly CPU optimization. It's possible that older Motorola devices might've done the same thing, but none of the newer devices we have on hand exhibited the behavior. It’s a systemic problem that seems to have surfaced over the last two years, and one that extends far beyond Samsung.
quote: It is a marketing gimmick and bragging rights to be the first to 64-bit ARM in a mobile device.