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arm processorsIf you’ve paid any attention to smartphones and tablets you’ve likely heard of the term “ARM” used to refer to the hardware inside. It’s thrown around left and right, often as a point of differentiation from laptops and desktops, which use Intel x86.

But what is ARM, exactly? A processor architecture? A brand of hardware? Or something else? That’s rarely explained. Let’s cut through the confusion and get down to the basics.

The Key To ARM Is RISC

arm processors

ARM is an acronym which stands for Advanced RISC Machine. In the name is another acronym (yes, nested acronyms!) which stands for Reduced Instruction Set Computing.

RISC is, in its broadest form, a design philosophy for processors. It stems from a belief that a processor with a relatively simple instruction set will be more efficient than one which is more complex. The term originally came into use back in the 1980s with a research project called Berkeley RISC that investigated the possibilities of this approach to design and then created processors based on it.

All ARM processors are considered RISC designs, but this doesn’t mean much because RISC itself is simply an approach to design rather than a technological standard or processor architecture.  Still, a basic understanding of RISC properly frames ARM.

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ARM’s Basics

what is an arm processor

ARM refers to itself as an architecture, which can cause a misunderstanding when compared to Intel. Intel gives every new chip design its own unique code and talks about each as a new architecture – even when there’s often many similarities and they all use the same instruction set (x86). ARM, on the other hand, treats its designs as an unbroken family. Updates are still a part of the ARM architecture. They’re just given a new version number.

The trait that’s most relevant to consumers is not the micro-architecture (the physical design of the chip) but instead the instruction set. The instruction set is the basic set of capabilities and features a processor makes available to software. It determines what arithmetic can be used, how cache should be allocated and the order in which instructions should be executed. Software designed for one instruction set can’t be used on another unless it’s revised.

Micro-architectures and instruction sets can’t be separated because the architecture is a physical expression of the instruction set.  This is why ARM-based processors tend to be small, efficient and relatively slow. The simple instruction set requires a small, simple design with fewer transistors. Transistors consume power and increase die size (which increases production cost), so having as few as possible is ideal when selecting a processor for a smartphone or tablet.

ARM’s Business Is Different

what is an arm processor

Talking about ARM processors as a whole can be difficult because there are so many available and their performance varies. It’s counter-intuitive. How can Apple have ARM processors that are quicker than the competition when it’s using the same architecture?

This happens because of how ARM Holdings, the company that is responsible for ARM, does business. ARM Holdings is only a design company. They manage the instruction set and design new versions of the core architecture and then license it to other companies. Those companies can then improve it and pair it with whatever hardware seems appropriate.

It helps to understand that ARM’s core architecture What Is A Processor Core? [MakeUseOf Explains] What Is A Processor Core? [MakeUseOf Explains] Every computer has a processor, whether it's a small efficiency pro or a large performance powerhouse, or else it wouldn't be able to function. Of course, the processor, also called the CPU or Central Processing... Read More is only a processor. It doesn’t handle wireless connectivity. It doesn’t handle graphics. It doesn’t handle USB USB 3.0: Everything You Need to Know USB 3.0: Everything You Need to Know USB 3.0 beats USB 2.0 in so many ways. Here's everything you need to know about why you should always pick USB 3.x when possible. Read More or other forms of wired connectivity. All of that is the responsibility of other hardware licensees pair the architecture.

That’s why there are so many variants of ARM on the market and why they perform differently. Apple has an entire in-house engineering staff that works on its ARM processors. Other companies, like Qualcomm and Texas Instruments, act as middle-men. They take the ARM architecture, pair it with a variety of hardware, and then re-sell it as a “system-on-a-chip” for smartphones and tablets.

What Does ARM Mean For Consumers

what is an arm processor

To a consumer, ARM can be thought of as an ecosystem. Software designed for ARM will only work on ARM. Windows RT What's The Difference Between Windows 8 & Windows RT? [MakeUseOf Explains] What's The Difference Between Windows 8 & Windows RT? [MakeUseOf Explains] With the Surface tablet announcement a few weeks ago and the final release of Windows 8 looming ever closer, some people are understandably going to be confused about the various versions available. I'm here to... Read More apps, for example, don’t work on a PC with Windows 8. Modifications must be made to a program to jump from ARM to x86.

Operating systems that work on one ARM device should work on others. This is why there are so many Android modifications and why Android can potentially be loaded onto tablets from HP and BlackBerry. Apple does mess with the ecosystem a bit, however, because the source code of iOS is not available. Attempting to port iOS to other ARM devices is almost impossible without it.

ARM also means lower power draw and lower performance relative to x86. This is not set in stone, however, because both architectures are changing over time. Intel is working hard to create versions of its processors with extremely low power draw. And ARM Holdings is working hard to improve the performance of its designs.

Will ARM Be In Your PC?

arm processors

There have been a few attempts to sell traditional devices with ARM processors that work like traditional PCs. Motorola sold a keyboard dock for the Atrix smartphone and advertised it as a laptop replacement. ASUS sells a line of Android tablets with keyboard docks.  And Samsung now sells a Chromebook What Is A Chromebook? [MakeUseOf Explains] What Is A Chromebook? [MakeUseOf Explains] Everything is moving towards the web, which is now more commonly being dubbed “the cloud”. As such, your devices should probably be ready and well equipped to make full use of cloud services for your... Read More that runs on ARM.

Such attempts foreshadow a storm of potential surrounding ARM, yet predicting the storm’s path and intensity is impossible. Current ARM architectures are significantly behind the performance Intel’s slowest processors (nevermind its mainstream line of Core processors). Nvidia says that it is working on a processor using ARM’s architecture that will compete with Intel, but it’s not clear how this is being accomplished or when a finished product might be released.

For now the potential threat of ARM remains a dark cloud on the horizon of the potential PC space. It looks threatening, but a concrete threat has yet to manifest. Is ARM a fearsome storm or simply a few shadowed clouds that will eventually disperse? That remains to be seen.

  1. Gary Mundy
    December 8, 2012 at 5:53 am

    Competition is good . It makes all of the manufacturers innovate.

  2. druv vb
    December 6, 2012 at 12:03 pm

    ARM is really in a good place to just kick back and relax. Most of its architectures are going in smartphones and tablets. And while they might be going for servers and stations, which may happen in the next five years, there are doing good business with their low cost processor architectures. First were single core, then a dual-core and now quad-core ARMs running on devices. Go on ARM, surprise us...

  3. Prasanth Mathialagan
    December 5, 2012 at 5:03 pm

    Excellent article.. Now I have clear idea about many things!!

  4. Vishal Srivastava
    December 5, 2012 at 4:27 pm

    Thanks a lot for explaining ARM to me. I was in need of this article!!

  5. Alexander
    December 5, 2012 at 1:55 pm

    Great and informative article :)

  6. Chris Hoffman
    December 5, 2012 at 11:12 am

    ARM is indeed something that could be powering laptops and other PCs -- witness the new Chromebook and talk about Apple switching to ARM for their Macs.

    That's why Windows RT's limitations are so terrifying. Goodbye ability to run desktop apps on laptops in the future! At least on Windows.

  7. susendeep dutta
    December 5, 2012 at 10:48 am

    This is very good article an is helpful for those who find it difficult to understand learning the technical aspects of ARM while searching online.

  8. Douglas Mutay
    December 5, 2012 at 9:10 am

    Thanks Matt. Very instructive indeed!

  9. vineed gangadharan
    December 5, 2012 at 6:51 am

    so if arm becomes wide spread for pc then every version of arm will have different set of application versions too???

  10. Anonymous
    December 5, 2012 at 6:31 am

    Thanks! I didn't realize that ARM had anything to do with RISC.

  11. Shubharup Ganguly
    December 5, 2012 at 4:24 am

    Thanks for the info! That was a good read.

  12. gpvprasad
    December 5, 2012 at 2:53 am

    Actually most of the times ARM is architecture but different companies use the architecutre and build their own flavours for little advancements, Hardly you will find ARM Processor, what you will find is ARM based processor

  13. Peter
    December 4, 2012 at 7:33 pm

    Excellent write-up. I'm still confused as to how Intel and AMD missed the boat on the low power cell/tablet market? But I also dry my ass and face with the same towel after a shower.

    • Matt Smith
      December 5, 2012 at 12:00 am

      To be fair to Intel and AMD it's not as if ARM had some master plan to make smartphones popular.

      They got lucky.

      The iPhone came out, smartphones caught on, then tablets - and ARM just happened to be in a much better position for that sort of thing than x86.

      If the smartphones never became a thing no one would be talking about ARM right now.

      • Peter
        December 5, 2012 at 12:18 am

        They got lucky? I don't think so Matt. Intel and AMD are huge organizations that have virtually unlimited funds- and they missed the market.

        When you're too big- you're too fat to make a move.

        Too big to innovate, too big to realize, too big to know. Epic fail.

        • Matt Smith
          December 5, 2012 at 12:42 am

          This is where you provide evidence that ARM Holdings knew the smartphones and tablets were coming, would be a huge hit, and intentionally positioned itself to serve that market beforehand. I'm willing to see such evidence but I've yet to see anything of the kind.

          Also, calling Intel too fat to move is absurd. They have been and are continuing to develop processors on a cycle far quicker than anyone else. Plus they have the best fabrication. Intel literally defines the cutting edge of processor technology.

        • Peter
          December 5, 2012 at 7:56 am

          Intel completely missed the low power processor market. Why is it so difficult for you to admit they missed the mark?

          Intel literally defines the cutting edge of processor technology- except in tablets and cell phones which is the fastest growing sector in consumer electronics.

          It's okay to admit failure.

  14. trevor mahon
    December 4, 2012 at 6:59 pm

    A very good article helps those like myself who are learning all the time to understand it all a bit better.Thank you.

  15. Ahmed Khalil
    December 4, 2012 at 6:11 pm

    i hear also apple comming labtops will depend on arm processors

  16. Gerald Huber
    December 4, 2012 at 5:50 pm

    Timely article. I was just reading a review for the Chromebook last night and was wondering about this ARM fella. Thanks for the info.

  17. Michael Jan Moratalla
    December 4, 2012 at 5:01 pm

    very informative and I really believe that it will truly be a storm. a storm strong enough to change the way of computing

  18. Garey Boone
    December 4, 2012 at 4:48 pm

    Thanks for the info I've been curious for a while now.

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