I remember the speculation that lead up to Apple's iPad launch. The list of things everyone expected the device to do was absurd, and the theories on the architecture behind Apple's first branded SoC was just as fantastic. The simplest answer is sometimes the right one and as Ars Technica's Jon Stokes pointed out, the A4 was nothing more than a hardened ARM Cortex A8 core running at 1GHz in the iPad (and 800MHz in the iPhone 4).

The Cortex A8 is something we've covered extensively here so I won't go into great detail right now. It's a dual-issue, in-order architecture with a 13 stage integer pipeline and a non-pipelined FPU.

When Apple announced the iPad 2, it also briefly announced the A5 SoC. The only detail given? The A5 is a dual-core processor with a GPU that's 9x faster than what's in the A4.

There are only two recent ARM architectures that have multicore support: the ARM11 and the ARM Cortex A9. The A8 doesn't come in a multicore variant. Given how many other SoC vendors are shipping dual-core Cortex A9 SoCs, the A5 was likely no different than NVIDIA's Tegra 2, TI's OMAP 4 or Samsung's Exynos in that regard: armed with a pair of Cortex A9s running at 1GHz. Update: Geekbench reports clock speed at 900MHz. Update 2: Apple confirms 1GHz clock speed on the iPad 2 specs page.

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

The Cortex A9 is similar to the A8 but with an out-of-order execution engine and a shallower pipeline (9 stages). The result is better-than-A8 performance at the same clock speed. The A9 also adds a fully pipelined FPU.

Now it's unclear what the rest of the A5 SoC looks like, but from the CPU standpoint I think it's safe to say that there are a pair of ARM Cortex A9s in there. We can look at the increase in Geekbench Floating Point scores for some proof:

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:

Linpack

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.

Memory size, bandwidth and operating frequencies are all unknowns that I was hoping to find out more about once I put hands on the iPad 2. 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.

SunSpider Javascript Benchmark 0.9

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:

Rightware BrowserMark

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).

2011 Page Load Test - Average

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.

The move to iOS 4.3 really narrowed the gap between the original iPad and the Xoom. In some cases the two actually render pages in the same amount of time, however that's typically for lighter pages that are easy to render. Up the complexity and the Xoom easily distances itself from the original iPad.

2011 Page Load Test - AnandTech.com

2011 Page Load Test - Amazon.com

2011 Page Load Test - CNN.com

2011 Page Load Test - Digg.com

2011 Page Load Test - Engadget.com

2011 Page Load Test - Facebook.com

2011 Page Load Test - NYTimes.com

2011 Page Load Test - Reddit.com

We'll touch on this more in the full review but it's not all about performance when talking about web browsing between the iPad 2 and the Xoom. Although the iPad 2 may have faster render times on average, the Xoom still supports tabbed browsing which definitely has its advantages.

Introduction The GPU: PowerVR SGX 543MP2
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  • ltcommanderdata - Saturday, March 12, 2011 - link

    Just divide out whatever whatever graphical benchmark result by resolution to get a relative power per pixel measure.

    On this subject, hopefully Anand can update this Preview with GLBenchmark results as soon as they are available rather than waiting for the Review. This will be a very interesting result and I think the SGX543MP2 can potentially be 3 times faster than Tegra 2 if the drivers are well optimized.
    Reply
  • slickr - Saturday, March 12, 2011 - link

    Please Adand could you tell me the point of this device?

    You can't carry it in the pocket, its not a gaming device, its not a texting/writing device, its not a office device, its worse than PC and laptops for everything and too big to have over a phone and not to mention no phone connectivity.

    So it seems to me its just a huge, bulky web surfing device and even mobile phones have a better camera so its not good even for pictures.
    Reply
  • stealthy - Saturday, March 12, 2011 - link

    This is exactly the device what I'm seeking. As most of the time in the evening I'm just websurfing/chatting with my girlfriend in Japan or emailing.
    I dont need to have a full blown pc to comfortably do this,
    The ipad is fully supported by my cable provider. I can program the digital box with the device and watch a second program in parallel to my tv. Easy to follow two soccer matches :)
    Apart from that I can control my home domotics system from my couch.

    All this is the reason for getting the ipad.
    Reply
  • Juzcallmeneo - Saturday, March 12, 2011 - link

    Most people just use it as a toy..or a trend.

    The purpose is to bring things like reading books, browsing web, casual games, movies, etc..to a more mobile state than a bulky laptop with a giant keyboard attached. You can easily cradle it in your arms and walk around with it..sit in any position. Smartphones are more mobile, but not as comfortable to use in the sense that the Tablets have nice large screens.

    They would be even more useful if they were all built like my new Eee Slate with the Wacom Digitizer technology on it. I do all of my computing on this thing now, especially all graphic & web design. The only downside is the battery life but it's good enough and worth it to have Office pro, CS5, and FL Studio on a tablet.
    Reply
  • name99 - Saturday, March 12, 2011 - link

    For me it's a device for reading technical PDFs. It does this far better than
    - a laptop (keyboard gets in the way)
    - a kIndle (PDF display is crap for technical PDFs, not to mention SLOW)
    - any Android device (faster, nicer screen, apps that handle the details, like margin cropping, well)

    If you doesn't do what you need, why not just STFU? I don't run around the web sites for fancy camping equipment saying "Well, who really needs this equipment? Why don't you just stay at home where it is more comfortable?"
    Reply
  • CAR67 - Saturday, March 12, 2011 - link

    LOL, thanks for making me laugh.

    I always think along the same lines as your reply when people piss and moan about how something is useless to them, so no body else should want one and so it should cease to exist.
    Reply
  • Azethoth - Saturday, March 12, 2011 - link

    Speaking purely of my original iPad :
    1) It paid for itself by replacing my NY Times habit at Starbucks with various free news apps (NY Times & BBC being my favorites).
    2) It made me fork over $100 for an Economist iPad subscription, doh. I really like the solid reporting they do.
    3) It controls both of my Squeezebox Touch music players with nice touch interfaces and glorious album covers ($10 SqueezePad app).
    4) Using the Calorie Counter app I have lost 10 pounds in the last 2 months. I could use it on the iPhone in theory but in that small a form factor ... just not gonna happen. Same on my comp, I am just not gonna run to the computer room every time I eat something, especially when not even at home. Another 20 pounds lost and I will be at a healthy weight: priceless.
    5) I love reading, a lot. But my place cannot handle more paper books. I have read books using iBooks and the Kindle app. The iPad is fantastic for reading at night or twilight. I even read outside in the Sun, but not with the sun relfecting off the pages. But thats ok, I do not read regular books with the Sun bouncing off their pages either. The only scenario not supported is reading in a nice warm bath: I cannot have my iPad get wet.
    6) Home automation. It is a niche thing but the iPad is a breakthrough interface in this arena. I am just getting started but I can control the furnace, a/c and fireplace so far.
    7) Free phone calls using skype & wifi.
    8) I use a small leather backpack to lug it around along with my coffee mug, water etc.
    9) It is a gaming device. My favorites are Plants vs Zombies, Infinity Blade and Osmosis. I have played more games on it than my XBox, although Kinect is changing that. It does not replace PC gaming, but it enables games not possible on the PC.
    Reply
  • slickr - Saturday, March 12, 2011 - link

    So it other words its just an expensive, huge and bulky device just for web surfing.

    In better times we would call people that purchase these things stupid, laugh at them for making a bad choice and educate them how to recognize true value for money and make a smarter purchase tomorrow.

    Guess times have changed for the worst, where the unacceptable is acceptable and the worthless is cool and trendy.

    Whats next they are going to invent a Stone 2.0 with WiFi and an apple picture of the back of it and people are going to shell out hundreds of dollars for the cool rock 2.0.

    Amazing, just freaking amazing.
    Reply
  • AlexTheUkrainian - Sunday, March 13, 2011 - link

    Sniff, sniff... can anyone else smell an angry troll?

    slickr, I am sure you're just trolling, or deeply jealous, but if not, just buy an iPad and see for yourself. It's frankly a device you can hear about a million times and never get it till you use it. There's just something magical about software always working, having an app for just about everything you can think of, and enjoying superb mobility, etc. Cooking? Just attach it to your kitchen cabinet and watch a video instructing how to make a dish. Taking notes in class - perfect companion! Want to connect to your windows pc remotely from your couch and still enjoy touch screen? Done.

    And yes, the games rock. And they'll rock 10 times as much once they learn to use iPad 2's power.

    TO ALL OTHERS: I just got hdmi adapter for this and I have to say, it's amazing for gaming! Now I can play and girlfriend can watch on big screen. But it's even better with games that don't require use of touch screen, such as Real Racing which can use just the accelerometer. Sooo recommend it. It's becomes a mobile xbox almost ha
    Reply
  • Shadowmaster625 - Monday, March 14, 2011 - link

    Yeah I'm sure slickr is just jealous. He wants to be a dumb yuppie. Some people live and die by these money black hole devices. As soon as you start paying for something due to its "coolness" factor, it's all over... Bottom line is these are $200 devices. They offer nothing vs an ipod touch, except the ability to hold it a bit further from your face. Reply

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