Why do they say Windows 8 devices running on ARM can’t support legacy applications?

Keefe Kingston May 18, 2012
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I read an article once saying they’ve officially named the version of Windows that will be running on devices with a ARM processor: Windows RT. Now, usually I wouldn’t care what processor was in my tablet-to-be, but then when I read an article, it said non-retro apps would not be ale to run on these devices, because they don’t have 32-bit support. Yet Wikipedia says it’s a something about it being based off of a 32-bit architecture architecture architecture.

So right now I’m confused on how many bits a actual ARM processor is (Because i know they mainly are 32-bit, 64-bit, and we will probably be looking at 128-bit soon), and how it’s except from the standardized bit system that is computer logic. Not only that, I’m kinda mad as well. I don’t want a half-witted version of Windows 8. I strongly believe that Windows 8 is best on a touch device (A keyboard and mouse is a nightmare to use /opinion), and so naturally I want one. But I’m a very demanding of my tech. I want it do what it’s supposed to, and more! And so if I’m getting a tablet, I want to be able to run the same programs my laptop does (which is a quite big and bulky gaming laptop…not very practical lugging around everywhere). When the iPad was only rumor, I was hoping it’d be like a thin Mac computer, only to be disappointed when it turned out to be an over-sized iPod touch.

Don’t get me wrong…I’m not saying the iPad is horrible at all, but I just want to see a tablet that can do more beyond it’s app store. And since Windows is the latest one, I was hoping they would revolutionize the tablet industry; bringing the full functionality of a PC to any car, train, bus, plane, or any other place you can think of. Anyways…enough of my ranting: Why can’t ARM devices run regular programs, if the architecture is based off a 32-bit processor?

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  1. Laga Mahesa
    May 18, 2012 at 11:40 pm

    Generally speaking, software must be built for a specific processor family: x86 (386, Pentium, Core2Duo, etc), Motorola, PowerPC, ARM, and so on.

    This is why Apple provided an emulation layer called Rosetta when they moved from PowerPC to Intel, which allowed the computer to pretend to have a PowerPC processor. Because this is emulation, the apps always run much slower, so people only installed and used it as a last resort.

    Matt Smith covered the 32 bit case neatly; essentially, that is a measurement of how much memory the system can access. 32 bit apps can run on a 64 bit operating system, but not vice versa.

    If you can find a tablet that has hardware that matches or bests the minimum requirements for your chosen operating system, your only stumbling block for installing said system on it is driver support.

    • Bruce Epper
      May 19, 2012 at 12:03 am

      The 32-bit and 64-bit issue is not a matter of how much memory the system can access, but the width of the address bus and data bus. The width of the address bus affects the amount of memory that can be accessed, but with some digital trickery a 32-bit processor can still address more than 2^32 bytes of memory. This was done with the old 16-bit processors before which would allow you to access 2^20 bytes of memory rather than just 2^16 bytes. The reason a 64-bit program cannot run on a 32-bit system doesn't have anything to do with the amount of memory that can be addressed but rather the fact that a 32-bit system can only transfer 32 bits of data in a single memory transfer when the program would be expecting to see 64 bits of data.

      • Mahesh
        July 19, 2012 at 5:49 pm


        As far as I know the windows 8 tablets are available on multiple processors & platforms. ARM is the cheapest one. Intel ATOM and AMD NEON will be the closest moderately priced tablets, and run desktop applications natively.
        You can always pay upwards of 1000 you will be able to get i3/i5 or Phenom if your concern is desktop compatibility.

        32 bit & 64 bit is not only the bus issue but CPU support issue. If any one remembers 486 SX / DX architecture. SX was essentially a 16 bit CPU able to run 32 bit programs with base address registers to get around using 16 bit wide bus for 32 bit addresses.

  2. Matt Smith
    May 18, 2012 at 11:03 pm

    ARM and x86 are fundamentally different instruction sets. Programs written for one can't talk to the other kind of processor. Unless you do some neat emulation tricks or re-write the program.

    32-bit is not an instruction set and isn't a factor in this issue.

    • Bruce Epper
      May 19, 2012 at 12:10 am

      Another consideration here is that Microsoft wants Metro apps on their tablet OS. There are a few exceptions (portions of their Office Suite) that will be redesigned to run on the WinRT desktop. Because of this, they are not incorporating an emulation layer to support legacy software. So if developers want their software to run on WinRT, they are forced to do a complete redesign for use on the WinRT desktop or to rewrite it for the Metro UI. With that decsion, Microsoft is hoping that developers will choose the latter rather than the former. I would imagine that with the next version, the desktop has the potential to be removed from their tablet OS if there is sufficient buy-in from the developer community (by releasing only Metro apps instead of WinRT desktop apps).

      • Keefe Kingston
        May 19, 2012 at 1:13 am

        Isn't there a problem then? If x86 and ARM are two different instruction sets, then that means developers have to make both versions for both devices. I hope some company that makes tablets would make one that'll give me the Windows 8 experience, while not loosing the functionality of a desktop. I still have alot of programs and games I'm attached to, and when I get a Windows tablet, I kinda want it to be like my 20 years of Windows experience, only with a touch screen. Thats why I jailbroke my iPod, so i can get more functionality out of it, and have things done my way, instead of what Apple thinks. Maybe people like me will need to jailbrake their Windows 8 device.

        • muotechguy
          May 19, 2012 at 7:43 am

          I think that if developers write for the Metro platform, it can be compiled to both ARM and x86.

    • Keefe Kingston
      May 19, 2012 at 1:01 am

      Ah...i see. Thank you! ^^

    • Emmanuel
      August 31, 2012 at 2:25 am

      Also on the low-level hardware side. The chip architecture is different from x86, 64 bit, MIPS types. Most of the time ARM cores are usually integrated in to a (SoC) which stands for System on Chip or (SiP) System in Package. These types of chips are usually custom designed chip packages that may contain the core cpu, power management, WLAN, transceiver, transmitter, antenna, GPU, Audio, Video etc. But thats not always the case for some devices. Usually chip and semiconductor manufactures will license the use of ARM Architecture in there packages.

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