Apple's iPad 2 Review: Tom's Goes Down The Tablet Rabbit Hole

Processor Performance: Now Dual-Core Flavored

Apple uses what’s referred to as a system-on-a-chip (SoC) in its mobile devices like the iPad and iPhone. In this particular implementation the SoC includes the processor core (or cores), graphics processing, and RAM in a package-on-package. Because those components sit next to each other in the same package, data transfers are achieved more efficiently. Moreover, less PCB space is consumed, since more functionality lives in one on-board component.

The influence of an SoC isn't all positive, however. A heavily integrated IC still has specific physical and thermal constraints, so the SoC's comprising subsystems aren't as potent as they might be if they were discrete.

Intel's Sandy Bridge architecture is a good example. The company simultaneously improved platform performance, while trimming power versus its previous-generation design. However, keeping processing, memory control, cache, and graphics in the same 95 W thermal window required concessions. The HD Graphics engine is perhaps the clearest indicator that Intel was working with a very specific transistor budget. Though the company's engineers created an engine deemed "good enough" for many desktop workloads, discrete graphics cards like AMD's Radeon HD 6970 and Nvidia's GeForce GTX 580 demonstrate how much more flexibility there is without the considerations afforded to more integrated solutions.


Apple A4 (iPad)
Apple A5 (iPad 2)
Processor
1 GHz ARM Cortex-A8 (single-core)
1 GHz ARM Cortex-A9 (dual-core)
Memory
256 MB LP-DDR (single-channel?)
512 MB LP-DDR2 (dual-channel)
Graphics
PowerVR SGX535 (single-core)PowerVR SGX545MP2 (dual-core)
L1 Cache
(Instruction/Data)
32 KB / 32 KB
32 KB / 32 KB
L2 Cache640 KB
1 MB


The iPad 2 features Apple's newest SoC, the A5, which is completely different from the A4 in its iPad. Let's start with what changes in the CPU.


ARM Cortex-A8
ARM Cortex-A9
Package Size
198.8 mm2238.8 mm2
Issue Width
dual-issue
multi-issue
Out-of-Order Execution
No
Yes
Execution Pipeline Depth
13-stages
8-stages
FPU
VFPv3
VFPv3
Processing Power
2.0 DMIPS/MHz/Core2.5 DMIPS/MHz/Core


Instead of the iPad’s ARM Cortex-A8, the iPad 2 uses a dual-core ARM Cortex-A9 with a total of 1 MB L2 cache. At the architectural level, the major difference is out-of-order execution. This is regarded to be a higher-performance approach than in-order execution, which executes instructions based on the order they appear. An out-of-order design addresses instructions based on the availability of of input data, thereby preventing the pipeline from spinning idly as data is retrieved.

If you want to draw a summertime analogy, consider the process of preparing a glass of ice water. You could choose to put the ice in the cup before you get the water, or you might fill the cup with water before getting the ice. The quickest task depends on where you are in relation to the refrigerator and the faucet. Out-of-order execution pipelines operate similarly.

The problem is that out-of-order execution requires extra die space in order to rearrange all those operations, which means that you're using more transistors and increasing energy consumption. That's one reason why Intel's small, power-efficient Atom architecture employs in-order execution. The benefit, however, is improved performance, as fewer CPU cycles are wasted. The fact that Apple moved to out-of-order execution is indicative of its emphasis on augmenting the iPad 2's performance.

According to analysis done by Chipworks, Apple also couples its dual-core ARM Corex-A9 with 512 MB of LP-DDR2 (low-power DDR2). The original iPad only used 256 MB of LP-DDR. So, not only do we have two times more memory, we have it delivered through a more modern memory technology (DDR versus DDR2).

ARM Cortex-A8ARM Cortex-A8

ARM Cortex-A9 (single-core variant)ARM Cortex-A9 (single-core variant)

CPU Performance

Geekbench is a synthetic benchmark similar to SiSoftware's Sandra, and it's one of the few available benchmarks available for iOS. The best part about Geekbench, however, is that it's offered on multiple platforms. That means we can use it to make apples to apples comparisons against low-power x86-based devices like netbooks.

Geekbench v.2
Score in Points, Higher is Better
Apple iPadApple iPad 2Dell Mini 1012
(Atom N450)
Overall
456
746
917
Integer
365
681
910
Floating Point
458
909
762
Memory
678
787
1105
Stream
325
323
1112


Single-threaded floating point and integer performance is much stronger on the iPad 2 than its predecessor. On average, performance nearly doubles.

The Cortex-A9 demonstrates a large lead in single-threaded scenarios due to its updated execution pipeline. However, threaded floating point performance sees an even larger boost, as the architecture's advantages are multiplied by the increased parallelism enabled by a second core. Though, I should point out that this doesn’t necessarily translate into better real-world performance. Most Apps have a greater tendency to rely on integer performance. That's the case whether you're talking about iTunes on the desktop or on the iPad.

From an architectural standpoint, we've come a long way since the original iPad debuted. But tablets fall very short of netbook-class performance. Intel's old Atom N450 still manages to outclass even Apple's latest hardware.

Geekbench v2 (detailed results)
Apple iPadApple iPad 2Dell Mini 1012
Integer Section
Blowfish (single-threaded scalar)13.6 MB/s13.2 MB/s26.2 MB/s
Blowfish (multi-threaded scalar)14.3 MB/s26.0 MB/s41.5 MB/s
Text Compress (single-threaded scalar)1.25 MB/s1.49 MB/s2.49 MB/s
Text Compress (multi-threaded scalar)1.20 MB/s2.79 MB/s3.60 MB/s
Text Decompress (single-threaded scalar)1.13 MB/s2.07 MB/s3.22 MB/s
Text Decompress (multi-threaded scalar)1.09 MB/s3.24 MB/s4.86 MB/s
Image Compress (single-threaded scalar)3.26 Mpixels/s3.77 Mpixels/s6.00 Mpixels/s
Image Compress (multi-threaded scalar)3.38 Mpixels/s7.42 Mpixels/s8.81 Mpixels/s
Image Decompress (single-threaded scalar)6.12 Mpixels/s6.66 Mpixels/s9.98 Mpixels/s
Image Decompress (multi-threaded scalar)6.04 Mpixels/s12.8 Mpixels/s15.0 Mpixels/s
Lua (single-threaded scalar)173.5 Knodes/s272.6 Knodes/s340.4 Knodes/s
Lua (multi-threaded scalar)172.9 Knodes/s535.0 Knodes/s488.4 Knodes/s
Floating Point Section
Mandelbot (single-threaded scalar)79.9 MFLOPS278.8 MFLOPS339.6 MFLOPS
Mandelbot (multi-threaded scalar)79.4 MFLOPS549.0 MFLOPS613.2 MFLOPS
Dot Product (single-threaded scalar)247.5 MFLOPS221.3 MFLOPS204.9 MFLOPS
Dot Product (multi-threaded scalar)246.2 MFLOPS435.5 MFLOPS361.5 MFLOPS
LU Decompression (single-threaded scalar)50.5 MFLOPS207.3 MFLOPS309.7 MFLOPS
LU Decompression (multi-threaded scalar)54.7 MFLOPS403.4 MFLOPS534.0 MFLOPS
Primality Test (single-threaded scalar)71.4 MFLOPS176.6 MFLOPS126.7 MFLOPS
Primality Test (multi-threaded scalar)69.2 MFLOPS316.8 MFLOPS194.5 MFLOPS
Sharpen Image (single-threaded scalar)1.51 Mpixels/s1.68 Mpixels/s482.1 Kpixels/s
Sharpen Image (multi-threaded scalar)1.52 Mpixels/s3.32 Mpixels/s858.9 Kpixels/s
Blur Image (single-threaded scalar)762.2 Kpixels/s664.4 Kpixels/s535.6 Kpixels/s
Blur Image (multi-threaded scalar)762.0 Kpixels/s1.31 Mpixels/s941.5 Kpixels/s


The write sequential and sfdlib write memory tests in Geekbench confirm better RAM performance, but it's difficult to separate how much of this is due to memory technology and how much is attributable to the processor. At the end of the day, it really doesn't matter; what does is that throughput goes up.

Intel's Atom N450 still manages to remain top dog, despite it's 64-bit single-channel interface. The Atom only falls behind in the sfdlib allocate and write tests. However, the N450's 1.97 GB/s score in read sequential is about 6x higher than what we see in the iPad 2.

Geekbench v2 (detailed results)
Apple iPadApple iPad 2Dell Mini 1012
Memory Score
Read Sequential (single-threaded scalar)306 MB/s342.2 MB/s1.97 GB/s
Write Sequential (single-threaded scalar)849.1 MB/s1.02 GB/s1.32 GB/s
Sfdlib Allocate (single-threaded scalar)1.99 Mallocs/s1.83 Mallocs/s1.25 Mallocs/s
Sfdlib Write (single-threaded scalar)1.28 GB/s2.57 GB/s1.34 GB/s
Sfdlib Copy (single-threaded scalar)830.4 MB/s474.8 MB/s1.03 GB/s
Stream Score
Stream Copy (single-threaded scalar)465.5 MB/s449.9 MB/s1.18 GB/s
Stream Scale (single-threaded scalar)320.5 MB/s372.5 MB/s1.08 GB/s
Stream Add (single-threaded scalar)655.9 MB/s606.3 MB/s1.41 GB/s
Stream Triad (single-threaded scalar)427.4 MB/s426.6 MB/s1.11 GB/s
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63 comments
    Your comment
  • What about adding other tablets in the mix?

    The XOOM could be a good choice, or the Asus Transformer.

    Cheers!
    3
  • We'll get to the others soon enough, but it's difficult to talk about other tablets without talking about Apple products.

    Cheers,
    Andrew Ku
    TomsHardware.com
    7
  • Samsung Galaxy 10.1 anyday.
    0
  • Here is the article where all the Apple fanboys start to tear this article up :).
    -6
  • Oops, sorry for the poor grammer :). Posted without rereading...

    Here is an article that Apple fanboys would be glad to rip up.
    3
  • gidgiddonihahHere is the article where all the Apple fanboys start to tear up .


    Fixed it for you. ;)
    2
  • Still no HDD expandability? No thanks. I'm not rich.
    1
  • Disagree.
    Like most computer guys like myself, adding an ipad won't make us to pack our PC/Mac to our closet. But again, mistakes like Microsoft or Linux, the "most computer guys on earth" are actually just a small group in total.
    For example:
    i've been teaching my 80 years old grandma to use pc to download, install and play simple games for years, no success. then she learned how to find/download/install/play many games after few days playing with my ipad.
    my 5 years nephew reads/plays/watch cartoons all on ipad now, she didn't turn on her pc for weeks.
    For myself, i uninstalled all my online video, movie client applications from my laptop, as I found watching these on ipad is much comfortable.

    Yes I still do my works on my pc, mostly in my office. At home, now the only thing force me to turn on my pc is to play world of warcraft
    I mean, who says ipad can't replace anything?
    2
  • joeyluDisagree.Like most computer guys like myself, adding an ipad won't make us to pack our PC/Mac to our closet. But again, mistakes like Microsoft or Linux, the "most computer guys on earth" are actually just a small group in total.For example:i've been teaching my 80 years old grandma to use pc to download, install and play simple games for years, no success. then she learned how to find/download/install/play many games after few days playing with my ipad.my 5 years nephew reads/plays/watch cartoons all on ipad now, she didn't turn on her pc for weeks.For myself, i uninstalled all my online video, movie client applications from my laptop, as I found watching these on ipad is much comfortable. Yes I still do my works on my pc, mostly in my office. At home, now the only thing force me to turn on my pc is to play world of warcraftI mean, who says ipad can't replace anything?


    I'd actually argue that in your case you're not replacing a PC, you're augmenting it. Granted, there will be others like your nephew and grandmother who can use an iPad as their primary device.
    3
  • May I simply say, "thank you" to Toms for writing a well thought out objective, honest and practical review of thr iPad2. Instead of getting carried away you've hit the nail on the head.

    P.s. I use an Acer W500 and I still struggle to justify why i have it.
    8
  • Good too see you guys are writing about tablets.Hope this trend continues and we can see reviews of more tablets :)
    5
  • In my opinion, the tablet is a fad that will go away when everyone finds out they are very cool looking toys that really don't add anything to what you can do.

    Oh, don't get me wrong; I think they'll make their permanent mark on the smart phone and laptop scenes, the devices that really fit into people's lives - but the tablet is too limited and too clumsy in actual use.

    Certainly, they have their niche uses - as book readers, like the Kindle, for example, but as something that will actually replace anything, I think not. Lots of coolz, little practicality.

    ;)
    2
  • What about light bleeding? I mean, the number of Ipads 2 that have this issue is staggering and has to be included in a review
    2
  • Marcus52In my opinion, the tablet is a fad that will go away when everyone finds out they are very cool looking toys that really don't add anything to what you can do.Oh, don't get me wrong; I think they'll make their permanent mark on the smart phone and laptop scenes, the devices that really fit into people's lives - but the tablet is too limited and too clumsy in actual use.Certainly, they have their niche uses - as book readers, like the Kindle, for example, but as something that will actually replace anything, I think not. Lots of coolz, little practicality.

    They don't "add anything to what you can do", but they do certain things much better than other devices.

    Reading this article on my iPad while sitting on a sofa was certainly much more comfortable than reading it on my desktop or laptop.
    2
  • molo9000They don't "add anything to what you can do", but they do certain things much better than other devices.Reading this article on my iPad while sitting on a sofa was certainly much more comfortable than reading it on my desktop or laptop.


    You need a more comfortable computer chair. =)
    0
  • Reading this article on a 108" projector screen was a lot more comfortable... :)
    4
  • molo9000They don't "add anything to what you can do", but they do certain things much better than other devices.Reading this article on my iPad while sitting on a sofa was certainly much more comfortable than reading it on my desktop or laptop.


    You should have taken the money you spent on your ipad and bought a more comfortable desk and chair for your desktop. Then a few cases of beer.
    -1
  • Spot on. Even Microsoft recognized that Windows Mobile applications had to be compatible with the full versions. Unfortunately there just wasn't the hardware to make it run....well....
    Oh, and using a stylus to type sucks.
    1
  • This is Boring, just like a tablet.
    -4
  • I only justify having a tablet for my girlfriend, who's work place (Hospital ER) will not allow laptop use during her down time, to browse or chat w/ me. But they do allow them to read books, or e-readers, so she has a nook color running Cyanogenmod7, so i guess the onl ytime a tablet is useful to us is when a laptop strictly isnt allowed.
    2