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  • Apple's A5: Two Cortex-A8s Under the Hood?


    The new A5 system-on-a-chip in the iPad 2 has been said to have a "dual-core" processor with "up to 2x" the power of its predecessor, the A4. However, if you review the actual words Steve Jobs used when announcing the new iPad, you'll note that he says "two processors inside" right after he reads "dual-core processors" off the slide. It's a meaningful distinction, because if "dual-core" meant a Cortex-A9 CPU, that would give the iPad 2 much more than "up to twice as fast on CPU performance." Given the low power draw of the new SoC, it's reasonable to speculate that what they've done is cram two low-power Cortex-A8s in there, rather than a single Cortex-A9.

    The graphics chip inside the A5 is widely assumed to be the PowerVR SGX543: with a render rate of 40 million polygons per second and a fillrate of 1 Gpixel/sec at 200MHz, this chip would certainly live up to the claim of "up to 9X faster graphics." However, all that extra processing draws power, and with battery life being held constant relative to the first-generation iPad, this would mean that power draw of the CPU has been dramatically reduced. A dual-core Cortex-A9 running in "power optimized" mode yields only 800 MHz, short of the 1 GHz claimed by Apple.

    Jobs claimed his "chip wizards" came up with the new A5 design, indicating that the team that was able to squeeze 67% faster clockspeed out of the iPhone 4 and iPad's single Cortex-A8 relative to the same chip in the iPhone 3GS may have been able to achieve the same feat with two A8s. The term "dual-core" usually refers to two processing cores on the same silicon die, but this is fairly loose terminology.

    What seems unquestionable is that Apple is going to route of pushing the speed and efficiency of ARM processors in its SoC designs, rather than going with off-the-shelf hardware. This gives a couple of advantage over the medium term. First, they can keep costs low by going with older chipsets rather than the latest-and-greatest technology. Secondly, when future SoCs do incorporate faster chips like the A9, they'll be able to squeeze more power out of them, and longer battery life than their competitors.

    Source: TiPB
    This article was originally published in forum thread: Apple's A5: Two Cortex-A8s Under the Hood? started by Paul Daniel Ash View original post
    Comments 33 Comments
    1. z3r01's Avatar
      z3r01 -
      o reily
    1. Cowboy's Avatar
      Cowboy -
      Hmm
    1. saunupe1911's Avatar
      saunupe1911 -
      Yes very interesting.

      Will someone please donate their iPad 2 to ifixit so they can dissect this thing and give the people the truth.
    1. z3r01's Avatar
      z3r01 -
      Quote Originally Posted by saunupe1911 View Post
      Yes very interesting.

      Will someone please donate their iPad 2 to ifixit so they can dissect this thing and give the people the truth.
      that wont be necessary as i kno they have money and will do this asap
    1. Cowboy's Avatar
      Cowboy -
      Quote Originally Posted by saunupe1911 View Post
      Yes very interesting.

      Will someone please donate their iPad 2 to ifixit so they can dissect this thing and give the people the truth.
      They will get one and tear it down within a few hours of release
    1. romeo_herman's Avatar
      romeo_herman -
      I don't know about this...
    1. Aaronius's Avatar
      Aaronius -
      It has also been speculated that since the A8 isn't inherently able to work in a multi processor environment and the A9 is, it would be reasonable to believe that Apple just put an underclocked A9 in there. They do have a history of underclocking processors to get better battery life, and it would probably be cheaper for them to put a single A9 in than try to rework the A8 to support multi processor environments.

      But, as was said upthread, we'll just have to wait for ifixit to do their thing.
    1. manickbarry's Avatar
      manickbarry -
      Seems strange I thought the graphics were on the same chip as the CPU so with 2 chips would that mean the graphics will be in sli mode lol
    1. iBwizzle's Avatar
      iBwizzle -
      Notion Adam > iPad 2
    1. krosis's Avatar
      krosis -
      The only dual-core A8 design out there that I'm aware of is Qualcomm's, so I guess it's possible that Apple "copied" them for the SoC this time around instead of Samsung like they did with the A4.

      Not that it matters much anyway.
    1. jOnGarrett's Avatar
      jOnGarrett -
      first we hear there are questions about the memory in the ipad 2 now we hear there is a mystery surrounding the processor(s)

      sound like some left over hardware apple had laying around so they decided to throw it into an ipad body along with a few modifications and call in an ipad 2.

      damn, Im so glad I never had any intentions of buying neither the ipad nor the ipad "2"
    1. z3r01's Avatar
      z3r01 -
      Quote Originally Posted by iBwizzle View Post
      Notion Adam > iPad 2
      any android device < iOs Device

      only reason your happy with that block of crap is what? because i know its not the Os running on it...android is ok but not EVEr getting close to any iOs....is it the ports? ur a port lover? ur gonna charge something on those ports while u charge the adam? double charging huh....thats smart...i own android devices and have to say...ANDROID is sooooooooooooooooooooooooo none user friendly and it feels bootleg after messing with an iOs device. my evo was just bought for 4G tethering...nothing more nothing less.
    1. CynicalDriver's Avatar
      CynicalDriver -
      Well, if it IS an underclocked A9...

      Would there be a way to reclock, or overclock it? I know Apple will not give us a way, but could it be done within the JB community? Or is this something that would require a new bootrom/flashing the chip itself?

      I would give up 2 hours or so of battery, for the faster speed, and I know I'm not the only one.


      Sent from my iPhone using ModMyi
    1. Johnboy00's Avatar
      Johnboy00 -
      The author's premise rests on an assumption that the batteries in the iPad and iPad 2 are the same. Where's that documented?
    1. z3r01's Avatar
      z3r01 -
      Where does it say that it's different?
    1. mori's Avatar
      mori -
      When steve sayd it and mr cook. And everyone else did. At 10hour. Same as iPad. Smh.
    1. krosis's Avatar
      krosis -
      Quote Originally Posted by Johnboy00 View Post
      The author's premise rests on an assumption that the batteries in the iPad and iPad 2 are the same. Where's that documented?
      Apple's site. Check the tech specs; it's still 25 Whr.

      Something to keep in mind from a technical perspective is that unlike desktop processors from 5-10+ years ago, modern mobile (and extending up into desktop) processors are very good at using very little power when they're not under load.

      Think about it this way, if you're watching a movie, and for every 10 seconds you watch, your processor has to wake up for 4 seconds to decode the movie, then it can go back to sleep (a crude approximation, but it works). Now if you have a dual core processor made on a newer, smaller manufacturing process, you may be able to decode that same 10 seconds of video in only 2 seconds, using only 75% of the power that the old chip used to do it in 4 seconds.

      Feel free to replace decoding a video with rendering a web page, an email, a PDF, whatever. Even if the CPU uses more power in bursts, if it gets the job done faster it can go back to sleep and let the user absorb the information. Now this means in turn that the user has less down time waiting for the device to respond, and is able to perform more tasks and use more cumulative processing power over time. This offsets the power savings of the smaller process (and whatever other improvements they've made) and apparently nets a similar life from a similar battery.
    1. brianiino's Avatar
      brianiino -
      hurry up and come out with a ipad 3D WORD!
    1. whereswaldo's Avatar
      whereswaldo -
      shouldn't it be called the A16
    1. warnera82's Avatar
      warnera82 -
      Yeah I can't wait for someone to tear this thing down!