The A5 processor is 800 Mhz. WHY?

Discussion in 'iPad' started by maxap, Mar 10, 2011.

  1. maxap macrumors 6502


    Sep 20, 2008
    So, it appears that the processor of the new iPad 2 (A5) is clocked at 800Mhz (if Geekbench could correctly identify its clock speed).

    How come it is so low? Is it underclocked? But why do Apple advertise it even on their website as 1Ghz dual-core processor?
  2. Pressure macrumors 68040


    May 30, 2006
    It, most likely, means that the clock speed is dynamic as it should be in a processor design.

    The A5 will run at up to 1 Ghz as advertised.
  3. Lagranger macrumors member

    Jun 22, 2010
    I'm not sure if you're getting the 800MHz figure from the Engadget review, but as Pressure stated, it may be that the processor speed is scalable or that GeekBench doesn't yet know know to measure the new CPU accurately. For example, here's another iPad 2 review (with an actual screenshot of GeekBench running) that shows the CPU speed as 894MHz. Granted, it's still not 1GHz, but it is much closer to 900MHz than 800MHz.

    Also, it's nice to finally have solid confirmation that the RAM size is 512Mb. 1Gb would have been great, but 512Mb is still better than 256Mb...
  4. maflynn Moderator


    Staff Member

    May 3, 2009
    Pick any one of these reasons
    • Apple has a long history of underclocking
    • Putting a dual core into the iPad and keeping the battery life the same
    • Dynamic stepping, i.e., increase/decrease the GHz rate depending on the need
    • Heat, perhaps the dual core package generates too much heat
    • Do we really know for sure what the speed will be because its not released yet
    • Do we really care what Ghz its running at, as long as the apps run.
  5. SandboxGeneral Moderator emeritus


    Sep 8, 2010
    The A5 is a dual core CPU and if it runs at 800MHz, then with two cores, you can effectively say it runs at 1.6GHz. That's because it can process twice the information at the same time at the slower speed.
  6. bbydon, Mar 10, 2011
    Last edited: Mar 10, 2011
  7. maflynn Moderator


    Staff Member

    May 3, 2009
    That's incorrect, you don't get 2x speeds when add a cpu core. There's overhead related to managing the threads. The apps and OS cannot fully divide the work up to spread it over the two cores. Its a fallacy to think that you get 2x the speed for dual cores or even 4x for quad cores. Its not linear .
  8. smiddlehurst macrumors 65816

    Jun 5, 2007
    Who cares?

    No, I'm absolutely serious, if the end user experience is noticeably improved without any cost to battery life (which all the current reviews seem to indicate is the case) why does it matter what the clock speed of the processor is? If the A5 really is running at 800Mhz (and I'm not convinced that's the case as others have said it could be a problem with the measuring tools or dynamic clock speed) what, exactly, is the problem with that?

    It's the same as that 'oh noes it doesn't have a GB of RAM, world ending stupidity from Apple' nonsense. Will the vast majority of users notice or care that it's not got it? Will it impact their experience with the device? No... so why must it form the basis for a thousand arguments the length and bredth of the internet?
  9. whocaresit macrumors 6502a

    Jul 18, 2010
  10. maxap thread starter macrumors 6502


    Sep 20, 2008
    What you state, is absolutely clear and anybody can understand the reasons for underclocking the CPU. However, I would like to know why Apple advertise the CPU speed as 1Ghz while it is not the case in practice. I think we all will see that it is indeed a dynamic speed and it will be able reach its maximum of 1 Ghz at some points.
  11. Diversion macrumors 6502a


    Oct 5, 2007
    Jacksonville, Florida
    Apple site says specifically "Dual Core 1ghz".. That should mean 1ghz x Two.

    We're probably seeing scaling cores here... or a mis-reporting geekbench..

    And or, an app needs to be coded to allow for the highest 1ghz slot in the kernel.. 1ghz dual core speeds might be reserved for apps that need the extra oomph. I'm fine with this, as long as the apps that need the power will be able to tap into it.

    Otherwise, if you're familiar with Android devices, might be just the kernel scaling back power when idle to save voltage going to the CPU.

    Nothing alarming here. This is where battery magic work.
  12. ZBoater macrumors G3


    Jul 2, 2007
    Sunny Florida
    The Xoom scales from 200mhz to 1.5ghz (rooted of course) so there is nothing strange here. Probably something wacky with the benchmark program. As long as I get 10 hours of battery and smooth kills at Infinity Blade, it can report 100mhz for all I care...
  13. camelsnot macrumors 6502


    Jan 31, 2011
    Yes. If you advertise it, it should be the specs as advertised. Yes apps will run.. hell, apps could run on a 600hz proc. That's not the point. They'll run a lot smoother, including future apps that will require more processing power, on a dual core 1Ghz processor which APPLE ADVERTISED. If the cores are scalable, fine. If they will never reach their full potential, then there is a problem.
  14. JRoDDz macrumors 68000


    Jul 2, 2009
    They also said the bus speed is twice that of the original at 200mhz. Faster memory access?
  15. Star-fire macrumors 6502

    Jul 4, 2007
    Which I'm sure it will run at when needed, almost every processor on the market will scale down at some point.

    Why are people so obsessed about specs, I can see it more on a full PC but on a tablet device, I could care less what's inside as long as it does what it's suposed to, it's not just towards apple either, it's more about what kind of device it is.
  16. BradClarke macrumors member

    Jul 1, 2008
    Im sure they our advertising correctly, I guaranty you its a 1Ghz Dual core, apple is pretty conservative with there numbers, its most likely idling at 800Mhz and it most likely uses the full potential when needed for apps like iMovie.

    They wouldn't lie about it, as apple would get ripped apart by all the blogs when ifixit takes it apart.

    It's like this, there is no point of using a processor at full speed when its not nessary, it like leaving my car running when Im not using it, would eat up all f my gas, I'm sure it the same with battery life if they let it consistently clock at 1GHz.
  17. dlewis23 macrumors 6502a

    Oct 23, 2007
    It dynamically adjusts the clock. The same thing that happens in your laptop will happen in the iPad. Lower the CPU clock to save battery till something needs to use it all.
  18. Davichi macrumors 6502

    Feb 23, 2011
    Go buy xoom. Enjoy paying 799 dollars. My MBA is only 850 dollars and it has dual core processor with 1.4GHZ. Adios...
  19. alent1234 macrumors 603

    Jun 19, 2009
    you have no idea what you're talking about. my core i5 CPU in my lenovo rarely goes above 10% and when i run a CPU-Z or whatever it's called it's reported to run lower than advertised frequency.

    this is done on purpose to save battery. no reason to run at a speed higher than necessary

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