The Apple iPad 2 Review
by Brian Klug, Anand Lal Shimpi & Vivek Gowri on March 19, 2011 8:01 PM ESTThe Right SoC at the Right Time: Apple's A5
Here's how I know Apple is masterful at marketing. After first showing off the new iPad Apple had tons of press convinced that the company was no longer competing based on specs but rather only interested in delivering an experience. In reality Apple is competing with hardware even more than before, it's just trying to give the public the impression that it's not. After all, Apple doesn't make the vast majority of the technology inside the iPad but it does control the experience. A competitor may be able to ship a dual core Cortex A9 but it can't ship the iOS experience. Is it really a surprise that Apple would downplay what it doesn't have exclusive rights to and instead try to get everyone to focus on what it does? Make no mistake, Apple is very much playing the specs game - in fact it's playing the game harder than anyone else in the industry today.
At the heart of the iPad 2 is a brand new SoC: the Apple A5. Built on what I assume is Samsung's 45nm process the A5 is a much more powerful SoC than it's predecessor the A4.
| Architecture Comparison | |||||||
| ARM11 | ARM Cortex A8 | ARM Cortex A9 | Qualcomm Scorpion | ||||
| Issue Width | single-issue | dual-issue | dual-issue | dual-issue | |||
| Pipeline Depth | 8 stages | 13 stages | 9 stages | 13 stages | |||
| Out of Order Execution | N | N | Y | Partial | |||
| FPU | Optional VFPv2 (not-pipelined) | VFPv3 (not-pipelined) | Optional VFPv3-D16 (pipelined) | VFPv3 (pipelined) | |||
| NEON | N/A | Y (64-bit wide) | Optional MPE (64-bit wide) | Y (128-bit wide) | |||
| Process Technology | 90nm | 65nm/45nm | 40nm | 40nm | |||
| Typical Clock Speeds | 412MHz | 600MHz/1GHz | 1GHz | 1GHz | |||
While the A4 featured a single core ARM Cortex A8, the A5 integrates two ARM Cortex A9s with a total of a 1MB L2 cache. That puts the A5 at a similar level of CPU performance to NVIDIA's Tegra 2 and TI's OMAP 4430. The only insider information I've managed to come across points to A5 featuring ARM's MPE (SIMD/NEON engine) in its A9 cores.
Based on Chipworks' analysis of the Apple A5 die it looks like Apple implemented a dual-channel LP-DDR2 memory controller, similar to TI's OMAP 4430.
| ARM Cortex A9 Based SoC Comparison | |||||
| Apple A5 | TI OMAP 4 | NVIDIA Tegra 2 | |||
| Clock Speed | Up to 1GHz | Up to 1GHz | Up to 1GHz | ||
| Core Count | 2 | 2 | 2 | ||
| L1 Cache Size | 32KB/32KB | 32KB/32KB | 32KB/32KB | ||
| L2 Cache Size | 1MB | 1MB | 1MB | ||
| Memory Interface | Dual Channel LP-DDR2 (?) | Dual Channel LP-DDR2 | Single Channel LP-DDR2 | ||
| NEON Support | Yes (?) | Yes | No | ||
Had it not been for NVIDIA Apple would've had the first shipping dual-core Cortex A9 SoC on the market. This is ultimately why Apple is producing it's own SoCs - most of the players in the SoC space don't seem to be moving fast enough for Apple's hardware schedule. Given the aggressive yearly product cadence I wouldn't be too surprised to see a dual-core Cortex A15 in the Apple A6 a year from now. Remember that much of Apple's success has come from being able to control it's hardware and software development. On the Mac side Apple has an extremely aggressive chip partner with Intel, but with the iDevices there is no equivalent (for now). Until that changes, Apple will continue to produce it's own SoCs. It's not that Apple is designing any of the IP that goes into the SoC, it's that Apple is piecing together what it needs, when it needs it.
We've already gone through the performance offered by the A5 over the A4, but to quickly recap: it's a huge increase. While the original iPad felt slow, the new one feels much faster. I would be lying if I said it was fast enough, but it's way better than the original.
CPU Performance
Taken from our iPad 2 Performance Preview:
| Geekbench 2 - Floating Point Performance | ||||
| Apple iPad | Apple iPad 2 | |||
| Overall FP Score | 456 | 915 | ||
| Mandlebrot (single-threaded) | 79.5 Mflops | 279.1 Mflops | ||
| Mandlebrot (multi-threaded) | 79.4 Mflops | 554.7 Mflops | ||
| Dot Product (single-threaded) | 245.7 Mflops | 221.7 Mflops | ||
| Dot Product (multi-threaded) | 247.2 Mflops | 436.8 Mflops | ||
| LU Decomposition (single-threaded) | 54.5 Mflops | 205.4 Mflops | ||
| LU Decomposition (multi-threaded) | 54.8 Mflops | 421.6 Mflops | ||
| Primality Test (single-threaded) | 71.2 Mflops | 177.8 Mflops | ||
| Primality Test (multi-threaded) | 69.3 Mflops | 318.1 Mflops | ||
| Sharpen Image (single-threaded) | 1.51 Mpixels/s | 1.68 Mpixels/s | ||
| Sharpen Image (multi-threaded) | 1.51 Mpixels/s | 3.34 Mpixels/s | ||
| Blur Image (single-threaded) | 760.2 Kpixels/s | 665.5 Kpixels/s | ||
| Blur Image (multi-threaded) | 753.2 Kpixels/s | 1.32 Mpixels/s | ||
Single threaded FPU performance is multiples of what we saw with the original iPad. This sort of an improvement in single-core performance is likely due to the pipelined Cortex A9 FPU. Looking at Linpack we see the same sort of huge improvement:
Whether this performance advantage matters is another matter entirely. Although there aren't many FP intensive iPad apps available today, moving to the A5 is all about enabling developers - not playing catch up to software.
Geekbench reports the iPad 2 at 512MB of memory, double the original iPad's 256MB. Remember that Apple has to deal with lower profit margins than it'd like with the iPad, but it refuses to cut corners on screen quality so something else has to give.
L2 cache size has also apparently increased from 512KB to 1MB. The L2 cache is shared among both cores and 1MB seems to be the sweet spot this generation.
| Geekbench 2 - Memory Performance | ||||
| Apple iPad | Apple iPad 2 | |||
| Overall Memory Score | 644 | 787 | ||
| Read Sequential (single-threaded scalar) | 340.6 MB/s | 334.2 MB/s | ||
| Write Sequential (single-threaded scalar) | 842.4 MB/s | 1.07 GB/s | ||
| Stdlib Allocate (single-threaded scalar) | 1.74 Mallocs/s | 1.86 Mallocs/s | ||
| Stdlib Write (single-threaded scalar) | 1.20 GB/s | 2.30 GB/s | ||
| Stdlib Copy (single-threaded scalar) | 740.6 MB/s | 522.0 MB/s | ||
Geekbench's memory tests show an improvement in effective bandwidth as well. The biggest improvement is in the stdlib write test which shows a near doubling of bandwidth from 1.2GB/s to 2.3GB/s. Unfortunately this isn't enough data to draw conclusions about bus width or DRAM operating frequency. Given the increases in CPU and GPU performance, an increase in memory bandwidth to go along with the two isn't surprising.
Geekbench shows a healthy increase in integer performance, both in single and multithreaded scenarios. The multithreaded advantage makes sense (two are better than one), but the lead in single threaded tests shows the benefit the A9 can deliver thanks to its shorter pipeline and ability to reorder instructions around stalls.
| Geekbench 2 - Integer Performance | ||||
| Apple iPad | Apple iPad 2 | |||
| Overall FP Score | 365 | 688 | ||
| Blowfish (single-threaded) | 13.9 MB/s | 13.2 MB/s | ||
| Blowfish (multi-threaded) | 14.3 MB/s | 26.1 MB/s | ||
| Text Compression (single-threaded) | 1.23 MB/s | 1.50 MB/s | ||
| Text Compression (multi-threaded) | 1.20 MB/s | 2.82 MB/s | ||
| Text Decompression (single-threaded) | 1.11 MB/s | 2.09 MB/s | ||
| Text Decompression (multi-threaded) | 1.08 MB/s | 3.28 MB/s | ||
| Image Compress (single-threaded) | 3.36 Mpixels/s | 3.79 Mpixels/s | ||
| Image Compress (multi-threaded) | 3.41 Mpixels/s | 7.51 Mpixels/s | ||
| Image Decompress (single-threaded) | 6.02 Mpixels/s | 6.68 Mpixels/s | ||
| Image Decompress (multi-threaded) | 5.98 Mpixels/s | 13.1 Mpixels/s | ||
| Lua (single-threaded) | 172.1 Knodes/s | 273.4 Knodes/s | ||
| Lua (multi-threaded) | 171.9 Knodes/s | 542.9 Knodes/s | ||
On average Geekbench shows a 31% increase in single threaded integer performance over the A4 in the original iPad. NVIDIA told me they saw a 20% increase in instructions executed per clock for the A9 vs. A8 and if we remove the one outlier (text decompression) that's about what we see here as well.
| Geekbench 2 | |||||||
| Overall | Integer | FP | Memory | Stream | |||
| Apple iPad | 448 | 365 | 456 | 644 | 325 | ||
| Apple iPad 2 | 750 | 688 | 915 | 787 | 324 | ||
The increases in integer performance and memory bandwidth are likely what will have the largest impact on your experience. The fact that we're seeing big gains in single as well as multi-threaded workloads means the performance improvement should be universal across all CPU-bound apps.
What does all of this mean for performance in the real world? The iPad 2 is much faster than its predecessor. Let's start with our trusty javascript benchmarks: SunSpider and BrowserMark.
Apple improved the Safari JavaScript engine in iOS 4.3, which right off the bat helped the original iPad become more competitive in this test. Even with both pads running iOS 4.3, the iPad 2 is 80% faster than the original iPad here.
The Motorola Xoom we recently reviewed scored a few percent slower than the iPad 2 in SunSpider as well. Running different OSes and browsers, it's difficult to conclude much when comparing the A5 to Tegra 2.
A bug in BrowserMark kept us from running it for the Xoom review but it's since been fixed. Again we're looking at mostly JavaScript performance here. Rightware modeled its benchmark after the JavaScript frameworks and functions used by websites like Facebook, Amazon and Gmail among others. The results are simply one aspect of web browsing performance, but an important one:
The move from the A4 in the iPad 1 to the A5 in the iPad 2 boosts scores by 47%. More impressive however is just how much faster the Xoom is here. I suspect this has more to do with Google's software optimizations in the Honeycomb browser than hardware, but let's see how these tablets fare in our web page loading tests.
We debuted an early version of our 2011 web page loading tests in the Xoom review. Two things have changed since then: 1) iOS 4.3 came out, and 2) we changed our timing methods to produce more accurate results. It turns out that Honeycomb's browser was stopping our page load timer sooner than iOS', which resulted in some funny numbers when we got to the 4.3/Honeycomb comparison. To ensure accuracy we went back to timing by hand (each test was repeated at least 5 times and we present an average of the results). We also added two more pages to the test suite (Digg and Facebook).
The iPad 2 generally loads web pages faster than the Xoom. On average it's a ~20% increase in performance. I wouldn't say that the improvement is necessarily noticeable when surfing most sites, but it's definitely measurable.
Double the Memory, Still Not Enough
On a Mac or PC if you don't have enough system memory and go to run a new application you'll get a lot of swapping to disk. The OS will write least recently used pages of memory to disk and evict them from main memory, making room for the newly launched application. Memory management in iOS works differently. All applications are required to save their state as soon as they move from the foreground as iOS can evict them from memory at any point in time.
Having more memory in iOS means you can have apps with larger memory footprints or you can keep more apps in memory without forcefully evicting them, but it generally doesn't mean you'll see improved performance.
With the iPad 2 Apple chose to only equip the device with 512MB of LP-DDR2 memory. That's half of what you get in the Motorola Xoom, but twice what you got in the original iPad. This does mean that (as we mentioned earlier) things like web pages can remain in memory longer, although there's no real impact on performance from what we can tell.
If Apple follows its short tradition, we may see more memory in the iPhone 5 and then more in the iPad 3 next year. Display resolution didn't increase so there's no pressure for additional memory there, but Apple is definitely holding developers back by not throwing even more hardware resources at the iPad 2.
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Anand Lal Shimpi - Monday, March 21, 2011 - link
The Xoom review was really written from the perspective of an iPad alternative, while I felt like we covered much of what made the iPad 2 different in our preview and wanted to focus on the bigger picture in the review.The Xoom's multitasking and notifications I believe make it easier to integrate into my workflow, but still not perfect. However Apple has been ergonomics than the Xoom, seemingly better (non-Flash) webpage compatibility, better stability and a smoother UI so it's a tradeoff.
Personally, I'd probably carry the iPad 2 thanks to improved ergonomics (especially with a smart cover) and non-smooth UI frame rates do bother me. But given my workflow neither is sufficient for me to use exclusively when traveling. That's why I mention that both camps have things to work on, whichever gets there first should get your money if you're really on the fence.
Take care,
Anand
Death666Angel - Sunday, March 20, 2011 - link
How do you get to the number in the chart? It would make sense to use the average of all 4 displays, but you don't seem to do that:406 + 409 + 352 + 354 = 1521
1521 / 4 = 380,25 ~ 380
Am I missing something here?
Also, the contrast should be 861:
966 + 842 + 778 + 859 = 3445
3445 / 4 = 861,25 ~ 861
Black levels should be better however:
0,42 + 0,45 + 0,49 + 0,41 = 1,77
1,77 / 4 = 0,4425 ~ 0,44
kmmatney - Sunday, March 20, 2011 - link
The point of having the numbers separate was to show the difference between the WiFi and "WiFi+3G" versions.Death666Angel - Monday, March 21, 2011 - link
And my question wasn't about that at all. The numbers in the actual charts they use for comparison against the iPad1 and the Xoom are not corresponding to any of the 4 distinct iPad2s. So I was wondering where they got the numbers from, if they averaged them or whatnot. If they did average them, then they made a few mistakes in the process. :-) If they got them through some other means it would still be interesting to know which they used.buff_samurai - Sunday, March 20, 2011 - link
speaking about workflow.
I am running a small consulting company for food/pharma industry, my expertise is in analytical instrumentation. Right now I'm using a beefy PC for CAD/backups and IP4/ipad for everything else: emails, project management, crm and documentation all squeezed into a small and portable device (terminal).
Although I am not 100% happy with exchange support in iOS, security, syncing etc I see myself more efficient then ever and that simply means more time/money in my pocket.
Lets try a common scenario: in a car, take a call, pull over, grab a laptop from a bag, power up, check some details, email couple of pdfs and do all that with customer hanging on the phone. Repeat the whole thing 10 times or more - you will see where I am coming from. Or try to carry your laptop around any mid size production line, control room and boardrooms and impress other engineers with questions like: 'where can I plug my laptop' at the same time.
I can understand that for most of heavy laptop users ipad is just useless but lets face the fact that there are millions of professionals on the road and all they care for is better response time and flexibility.
I could spend hours listing applications where no PC (portable or not) can match a tablet but the bottom line is: when moving to new tech we need to overcome our habits first. ipad, xoom and other are like a nice and shiny screwdriver but you will never find a use for it with pockets full of nails. That means no reviewer should ever comment on any device without actually making it a primary tool for couple of months: and if there is no time/money for it - just focus on things that are traceable or you may use your reputation.
darwiniandude - Sunday, March 20, 2011 - link
I always love Anandtech reviews, they cover 'everything' really well, advantages and flaws with equal gusto.Thanks!
Two points:
1) Page 19 I think you're referring to iDisk, not iDrive. Doesn't really matter unless someone trys to Google it.
2) With regard to web browsing, I know you're comparing these units as shipped, but I strongly recommend pro users consider 'iCab' from the AppStore, I don't use Safari much anymore. Propper tabs, full screen, downloading, browser user agent ID spoofing, way more powerful. Scroll pad to quickly navigate huge pages, gestures etc. Tt's very anti-iOS in that it's insanely powerful rather than designed to be simple, but I love it, specifically options like 'open bookmark in new tab' and 'open links from different domain in new tab' very customisable, plugins, blah blah blah. Anyway. It has Desktop style tabs. I wouldn't suggest you change the article, or review this or other 3rd party browsers because it's kinda beyond the scope of the review of the device, but it would be nice if people knew there were alternatives to give a more desktop style (still sans-flash) browser.
pja - Sunday, March 20, 2011 - link
I have really wanted an iPad ever since they were released. Several months ago I had the money (the previous barrier to acquisition) so I went looking. I didn't want the 3G version, WiFi would be fine. But I knew I would not be happy unless I got the one with maximum ram. Well in Australia that was going to cost me over AUD1,000 (I thought they were much cheaper :-( ).Just before this I had built myself a new desktop with an AMD processor and graphics card; see I'm a fan of AMD (but not a bigot). So might I be better off with a netbook rather than an iPad. AMD had recently released the Brazos range. So I started to do some research.
The result was my purchase of a Toshiba NB550D (the sexy orange one) which is a "little under-done" with the C50 Fusion Processor, only 1 Gb of memory and Windows 7 Starter. I have upgraded the memory to 2 Gb (still not enough) and installed Windows 7 Home Pro.
The Toshiba is about the same size as an iPad but is much more functional, it has all my desktop PC's apps installed (particularly my favourite text editor (EditPlus), my browser (Firefox) and all the same bookmarks, etc. etc.) so when I travel I have everything I need and I didn't need to learn how to use new software.
I still think the iPad is a great bit of gear but that's when I use the right side of my brain. My left side says "where's the value proposition?" We are all different but for me the left side of my brain always tends to win over the right side. I am very happy with "my" iPad alternative; more memory and the C-350 processor would be good (but not the larger form=factor that seems to entail). Oh! I forgot to say that the total cost of the Toshiba (including hardware and software upgrades was about AUD675 - more than AUD325 saving!
Regards,
Peter
Deepcover96 - Sunday, March 20, 2011 - link
Great review. Anandtech's reviews are always well worth the wait. They are always thorough and I always learn something. I agree that it is a luxury device and it is hard to justify it for getting work done. I still purchased an iPad 1. I recently sold it to buy the iPad 2, as soon as I can find one. I do think you downplay how important the app selection is on iOS as compared to Android.name99 - Sunday, March 20, 2011 - link
Reading the summary of what all three authors think of iPad feels to me like someone who buys an iPod because it has calendar and contact functionality, and then is upset/surprised that it isn't a Palm.iPad is not a REPLACEMENT for a laptop/desktop, it is an AUGMENTATION. You use each for what they are good at. If you find yourself spending most of your time traveling and you need a full-featured computer during that time then, sure, adding iPad to the mix is stupid. But if you already have a laptop, and can afford it, iPad makes certain tasks a lot more pleasant.
For my part, for example, my primary use for iPad is reading technical PDFs using Good Reader. I could read these on a laptop, but the keyboard really gets in the way (not to mention that the aspect ratio of the screen is inappropriate). If you don't do much reading of technical PDFs, this might seem dumb to you --- but I DO spend many hours a day reading these PDFs and I appreciate a tool that does the job properly, just like a professional carpenter doesn't use a $5 saw he bought at Walmart.
The future of computing is not one device that does everything; it is multiple devices all optimized to a particular human form factor, that all work together --- an iPod nano AND an iPhone AND an iPad AND a laptop AND a desktop. Criticism of something germane to this vision is legitimate and sensible (and Apple's flailing regarding how much of the file metaphor it wants to present to users is a legitimate part of this criticism.) But complaints whose primary structure is "this device doesn't work exactly like a device I already own" is just stupid --- like complaining that a bicycle isn't a car.
It's perfectly reasonable to say that you don't have a use for a certain class of device, especially because you already use something more powerful. I, for example, have no use for a Tivo or a video streaming devices like WD Live or Roku --- I have a full-fledged computer hooked up to my TV. But it is unreasonable to go further than that, and I've observed plenty of non-techy people who are very happy with their WD Live's or Tivos.
It's even more unreasonable to complain that "Tivo sucks because it doesn't play DVDs".
Use some sense. Don't keep trying to use iPad for things it is no good at. Keep in the bedroom, and use it to read, or to look up something quickly on the net, or to play a movie just before you go to sleep. Don't be insane and try to write a novel on it.
pja - Monday, March 21, 2011 - link
"iPad is not a REPLACEMENT for a laptop/desktop, it is an AUGMENTATION. You use each for what they are good at. If you find yourself spending most of your time traveling and you need a full-featured computer during that time then, sure, adding iPad to the mix is stupid. But if you already have a laptop, and can afford it, iPad makes certain tasks a lot more pleasant."You must have either too much cash or too much time on your hands or both. A good business class laptop is AUD1,500+ while a top of the range iPad is AUD1,000 + here in Australia.
It seems to me when you think about the iPod with your left brain there is very little functionality that a good netbook does not do both better and cheaper. However, I would agree that when you let your right brain rule then all of a sudden the iPad becomes a irresistible thing that you must possess. Unfortunately for me my left brain clicks in when I pull out my credit card.
Peter