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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. brbortscheller's Avatar
      brbortscheller -
      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.
      Why don't you? You don't have an extra $499.99 laying around? Guess what: NEITHER DO ALOT OF PEOPLE!
    1. StealthBravo's Avatar
      StealthBravo -
      There is no need to donate. They buy them for marketing.
    1. steve-z17's Avatar
      steve-z17 -
      Regardless whats in it, the faster speed will be great!
    1. StealthBravo's Avatar
      StealthBravo -
      Well the reviews have looked hopeful for sure.
    1. 4n4c0nd4's Avatar
      4n4c0nd4 -
      I can see Apple using Dual Cortex-A8s as a possibility. Didn't they have the option of dual PowerPC processors in the MacG3/4/5s when dual processor setups were mainly used in servers at the time?

      If the above information is incorrect, please correct me and accept my apologies. I'm not too familiar with Apple products offered back then.
    1. iSteed's Avatar
      iSteed -
      agreed on knowing the truth! lol
    1. NessLookAlike's Avatar
      NessLookAlike -
      So like the OP said, its possible that Apple's shoved a dual-core A9 in there that will run at 800MHz in its most power efficient mode -- but like krosis pointed out, a dual-core processor can be more power efficient than a single-core at the same speed if its used for a smaller amount of time to perform the same task. Couple that with, say, the ability of the processor to clock up from 800MHz to 1GHz under load (which doesn't happen often, honestly..) and some power-management tweaks under the hood and you're looking at a faster beast with similar power performance to the iPad's SoC. Apple could get away with using off-the-shelf Cortex A9's if they tweaked the system in just the right way.

      Another possibility: iPad 2 runs in 1GHz dual-core mode until 20% of the battery is left, and then clocks down to 800MHz.
      Another possibility: for the most part, the dual-core processor relies strongly on a single core most of the time and lets the other core sleep except when under heavy load, giving the iPad 2 the ability to run with all the speed of the single-core we're all used to but have the opportunity to perform faster under load.

      And even if it could only achieve 95% as much battery life as the single-core, I doubt Jobs would go up on stage and say 95% -- he'd say 100%. It's good PR.
    1. CaptainChaos's Avatar
      CaptainChaos -
      Quote Originally Posted by z3r01 View Post
      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.
      I used to think the same thing about the Android OS and I hate to say this, but your Evo's OS is yesterdays news. The iPad will be blazing with this chip. It will make a huge difference in the future. Right now there isn't much demand for the chip, but with the increases in functionality that Apple keeps adding it is going to be top notch.
    1. Eagleye's Avatar
      Eagleye -
      Quote Originally Posted by CaptainChaos View Post
      I used to think the same thing about the Android OS and I hate to say this, but your Evo's OS is yesterdays news. The iPad will be blazing with this chip. It will make a huge difference in the future. Right now there isn't much demand for the chip, but with the increases in functionality that Apple keeps adding it is going to be top notch.
      Dude, he was sayin exactly what you said... that the Android Evo OS is not very user friendly and IS yesterday's news. Did you miss the whole beginning to his post where he said "any android device < iOs Device" That means iOS is greater than "any andoid device"...Remember the Alligator "<" eats the greater device. Nom nom <<< iOS.
    1. CaptainChaos's Avatar
      CaptainChaos -
      Quote Originally Posted by Eagleye View Post
      Dude, he was sayin exactly what you said... that the Android Evo OS is not very user friendly and IS yesterday's news. Did you miss the whole beginning to his post where he said "any android device < iOs Device" That means iOS is greater than "any andoid device"...Remember the Alligator "<" eats the greater device. Nom nom <<< iOS.
      I really appreciate the math lesson lol but what I am saying is that Android has moved forward to a much better OS so he is doing himself a huge disfavor by judging Android by the Evo. I love iOS as well, but Honeycomb can not be scoffed at. I shrugged off Android until recently. I highly recommend it now.
    1. Assassination's Avatar
      Assassination -
      Hmmm A5 seems like a big graphics upgrade not speed. So basically when iOS 5 comes out it won't be that slow and have majority of the handy features
    1. EskimoRuler's Avatar
      EskimoRuler -
      Either waits great to get soMe speed improvements
    1. djdraco's Avatar
      djdraco -
      Speed baby. But does this mean the price will rocket like the gas prices?