While working on our Haswell piece, I've been religiously checking the Geekbench and GLBenchmark results browsers to see if anyone ran either benchmark and decided to tap upload. This usually happens before every major smartphone launch, but in the case of the iPhone 5 the details these applications can give us are even more important.

Yesterday we confirmed that Apple is using its own custom designed ARM based CPU cores in its A6 SoC. Apple opted not to design in a vanilla ARM Cortex A9 likely to avoid relying on pure voltage/frequency scaling to improve performance, and chose not to integrate a Cortex A15 likely because of power consumption concerns as well.

There's absolutely no chance of Apple sending us a nice block diagram of the A6 CPU cores, so we have to work with what clues we can get elsewhere. Geekbench is particularly useful because it reports clock speed. Why does clock speed matter? Because, if reported accurately, it can tell us a lot about how the A6's CPU design has improved from an IPC standpoint. Remember that clock speed doesn't matter, but rather the combination of clock frequency and instructions executed per clock that define single threaded performance.

Apple iPhone 5 Models
iPhone 5 Model GSM/EDGE Bands WCDMA Bands CDMA 1x/EVDO Rev.A/B Bands LTE Bands (FCC+Apple)
A1428 "GSM" 850/900/1800/1900 MHz 850/900/1900/2100 MHz N/A 2/4/5/17
A1429 "CDMA" 850/900/1800/1900 MHz 850/900/1900/2100 MHz 800/1900/2100 MHz 1/3/5/13/25
A1429 "GSM" 850/900/1800/1900 MHz 850/900/1900/2100 MHz NA 1/3/5 (13/25 unused)

A short while ago, Geekbench results for a device identifying itself as an iPhone5,2 appeared. Brian believes this is likely the A1429 Verizon device (A1428 being iPhone 5,1) - perhaps one presampled to a reviewer looking to test their luck.

MacRumors appears to be first on the scene, having been tipped by an employee at PrimateLabs (the creators of Geekbench). I need to preface the rest of this post with a giant caution sign: I have no inside knowledge of whether or not these results are legitimate. They seem believable, but anything can happen. The rest of this post is simply my initial thoughts on what these mean, should the results be accurate. Update: The first iPhone 5 reviews are out and this Geekbench data looks accurate.

Cache sizes haven't changed, which either tells us Apple isn't feeling as generous with die size as perhaps it once was or that working sets in iOS are still small enough to fit inside of a 1MB L2. I suspect it's mostly the latter, although all microprocessor design is a constantly evaluated series of tradeoffs (often made through giant, awesomely protected spreadsheets). 

The first real change is clock speed. Apple clocked its A4 and A5 CPU core(s) at 800MHz, although these Geekbench results point to a 25% increase in frequency at 1GHz. Some of the headroom is likely enabled by the move to 32nm, although it's very possible that Apple also went with a slightly deeper pipeline to gain frequency headroom. The latter makes sense. We've seen conservative/manageable increases in pipeline depth to hit frequency targets and improve performance before. 

The fairly low clock speed also points to an increase in IPC (instructions executed per clock) over the Cortex A9 design. As I mentioned in our A6 analysis post, simple voltage/frequency scaling is a very power inefficient way to scale performance. A combination of IPC and frequency increases are necessary. If these results are accurate and the CPU cores are only running at 1GHz, it does lend credibility to the idea of a tangibly wider design.

It's also unclear if Apple is doing any sort of dynamic thermal allocation here, ala Intel's Turbo Boost. You can't get more power constrained than in a smartphone, and power gating is already common within ARM based SoCs, so that 1GHz value could be under load for both cores. A single core could run at higher frequencies for short bursts. 

The next thing that stood out to me was the memory data:

Geekbench Comparison
Memory Performance iPhone 4S iPhone 5 (unconfirmed) Scaling
Read Sequential ST 0.32 GB/s 1.78 GB/s 5.63x
Write Sequential ST 0.86 GB/s 1.35 GB/s 1.57x
Stdlib Allocate ST 1.44 Mallocs/s 1.92 Mallocs/s 1.33x
Stdlib Write 2.7 GB/s 6.06 GB/s 2.24x
Stdlib Copy 0.55 GB/s 2.26 GB/s 4.13x


Geekbench Comparison
Stream Performance iPhone 4S iPhone 5 (unconfirmed) Scaling
Stream Copy 0.42 GB/s 1.9 GB/s 4.55x
Stream Scale 319 MB/s 994 MB/s 3.11x
Stream Add 0.59 GB/s 1.39 GB/s 2.34x
Stream Triad 377 MB/s 1019 MB/s 2.70x

It's well known that ARM's Cortex A9 doesn't have the world's best interface outside of the compute core and its memory performance suffered as a result. If this data is accurate, it points to significantly overhauled cache and memory interfaces. Perhaps an additional load port, deeper buffers, etc...

Also pay close attention to peak bandwidth utilization. The 4S had 6.4GB/s of theoretical bandwidth out to main memory, the 5 raises that to 8.5GB/s. In the Stdlib write test the 4S couldn't even hit 50% of that peak bandwidth. The iPhone 5 on the other hand manages to hit over 70% of its peak memory bandwidth. I will say that if these numbers are indeed faked, whoever faked them was smart enough not to violate reality when coming up with these memory bandwidth numbers (e.g. no 95% efficiency numbers show up). It's also clear that these results aren't a simply doubling across the board over the 4S, lending some credibility to them.

Some of the largest performance improvements promised by the Geekbench data appear here in the memory results. It's whatever work Apple did here that helped enable the gains in the integer and floating point results below:

Geekbench Comparison
Integer Performance iPhone 4S iPhone 5 (unconfirmed) Scaling
Blowfish ST 10.7 MB/s 23.4 MB/s 2.18x
Blowfish MT 20.7 MB/s 45.6 MB/s 2.20x
Text Compress ST 1.21 MB/s 2.79 MB/s 2.30x
Text Compress MT 2.28 MB/s 5.19 MB/s 2.27x
Text Decompress ST 1.71 MB/s 3.82 MB/s 2.23x
Text Decompress MT 2.84 MB/s 5.60 MB/s 2.67x
Image Compress ST 3.32 Mpixels/s 7.31 Mpixels/s 2.20x
Image Compress MT 6.59 Mpixels/s 14.2 Mpixels/s 2.15x
Image Decompress ST 5.32 Mpixels/s 12.4 Mpixels/s 2.33x
Image Decompress MT 10.5 Mpixels/s 23.0 Mpixels/s 2.19x
Lua ST 215.4 Knodes/s 455 Knodes/s 2.11x
Lua MT 425.6 Knodes/s 887 Knodes/s 2.08x
MT Scaling 1.90x 1.92x  

On average we see around 2.2x scaling from the 4S to the 5 in Geekbench's integer tests. There's no major improvement in multicore scaling, confirming what Geekbench tells us that we're looking at a two core/two thread machine. 

The gains here are huge and are likely directly embodied in the performance claims that Apple made at the iPhone 5 launch event. Many smartphone workloads (under Android, iOS and Windows Phone despite what Microsoft may tell you) are still very CPU bound. Big increases in integer performance will be apparent in application level improvements.

Don't be surprised to see greater than 2x scaling here even though Apple only promised 2x at the event. Remember that what you're looking at is raw compute tests without many of the constraints that apply to application level benchmarks. While Apple has used benchmarks in the past to showcase performance, all of its performance claims at launch were application level tests. Those types of tests are more constrained and will show less scaling. That being said, I am surprised to see application level tests that were so close to the 2.2x average scaling we see here. Apple could have moved to faster NAND/storage controller here as well, which could help most if not all of these situations.

Geekbench Comparison
Floating Point Performance iPhone 4S iPhone 5 (unconfirmed) Scaling
Mandelbrot ST 223 MFLOPS 397 MFLOPS 1.77x
Mandelbrot MT 438 MFLOPS 766 MFLOPS 1.74x
Dot Product ST 177 MFLOPS 322 MFLOPS 1.81x
Dot Product MT 353 MFLOPS 627 MFLOPS 1.77x
LU Decomposition ST 171 MFLOPS 387 MFLOPS 2.25x
LU Decomposition MT 348 MFLOPS 767 MFLOPS 2.20x
Primality ST 142 MFLOPS 370 MFLOPS 2.59x
Primality MT 260 MFLOPS 676 MFLOPS 2.59x
Sharpen Image ST 1.35 Mpixels/s 4.85 Mpixels/s 3.59x
Sharpen Image MT 2.67 Mpixels/s 9.28 Mpixels/s 3.47x
Blur Image ST 0.53 Mpixels/s 1.96 Mpixels/s 3.68x
Blur Image MT 1.06 Mpixels/s 3.78 Mpixels/s 3.56x
MT Scaling 1.96x 1.92x  

The floating point benchmarks show "milder" scaling in the first few tests (sub-2x) but big scaling in the latter ones. My guess here is we're seeing some of the impacts of increased memory bandwidth at the end there. If you look at our iPhone 5 hands-on video you'll see Brian talking about how super fast the new flyover mode in iOS 6 Maps is on the 5 compared to the 4S. That's likely due in no small part to the improved memory interface.

Although Geekbench is cross platform, I wouldn't recommend using this data to do anything other than compare iOS devices. I've looked at using Geekbench to compare iOS to Android in the past and I've sometimes seen odd results.

I'm sure we'll learn a lot more about the A6 SoC over the coming days/weeks. 

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  • amdwilliam1985 - Monday, September 17, 2012 - link

    "So you are saying that iPhone 5 is 'too light'."
    Yes, that's right, iPhone 5 is too light. You won't believe how many people said S3 is too light as a negative point against iPhone 4S. Now that iPhone 5 is lighter, it will produce the inferior product feeling. Of course, iSheeps always back track and find other arguments. "Oh yes, 3.5" is perfect. " turns to "hell yea, 4.0" is the king." LOL

    Let's not forget how "inefficient" Apple utilize their phone. We're only comparing screen sizes here, 3.5" to >4.5" screens of most Android phones. We forget to compare the actually size of the phone. iPhones are large phones with tiny screens by many standard. My gf's iPhone 4S is only fractionally smaller than my 4.5" TMobile SGS2 in terms of physical size.
  • KPOM - Tuesday, September 18, 2012 - link

    As soon as you use the word 'iSheep," you've lost the argument.
  • Stas - Sunday, September 23, 2012 - link

    You like a lighter phone...
    I found my SGSII too light. It was too hard to operate with one hand, as it didn't stay put - due to light weight it would slide easily. Grippy case helped, but I would prefer extra 15-20 grams.

    So you're saying Apple purposely makes a fragile device to feed the 3rd-party companies? You're delusional.
  • robinthakur - Monday, September 17, 2012 - link

    I quite liked the lightness of the S3 despite its cheap construction, so the fact that the metal IP5 is actually LIGHTER than the S3 is mind boggling to me. Agree that you reach diminishing returns at some point though. I'd like a bigger battery in there, but whenever they do something like that a la iPad3, all the whiners and Android jihadists come out in force. I think the iPhone will still be a bit more fragile than the S3 though, as even though it won't crack if you drop it, it will dent now. I suppose that is better, but the best solution as with any phone is "don't drop it" without a cover on. I've dropped my 4S a few times onto concrete from standing height, and the case has prevented any damage to it.
  • KitsuneKnight - Monday, September 17, 2012 - link

    I've dropped (more like tossed, since it flew out of my hand after tripping) my 4S a few times on concrete, without a case, and it survived perfectly fine. There's a couple scratches on the metal band on one corner, but you'd never notice without inspecting it closely. Luck probably played a bit of it, but it's certainly not super fragile as people like to imply.
  • lilmoe - Monday, September 17, 2012 - link

    spoken like a true fanboy... no use arguing with you.
  • doobydoo - Tuesday, September 18, 2012 - link

    spoken like a true fanboy... no argument was presented by you.
  • reddog007 - Monday, September 17, 2012 - link

    That is the key word for battery life: Advertised!

    SGS3 is not a brick, far from it. How is 20grams heavier than the iPhone 5 a brick? It is one of the lightest, if not the lightest Droid phone with the largest screen before being a phablet.

    I guess that the iPhone 4S is one small fat brick then. Screen is 1.8" smaller with a much smaller battery and the thing still weighs more.

    Yeah, it is taller and wider, but lets think here. Oh yea, it has a 0.8" larger screen. Wouldn't that be why it is taller and wider?!

    Ok, yep the SGS3 is fatter, but also just by 1mm. Im actually surprised that it isn't more because the new LCD tech Apple uses plus the nonremovable battery.
    If you wanna get a little more technical in terms of who is more a brick, lets take screen size into account. SGS3 actually weighs less per inch of screen then the iPhone5. SGS3 is more than likely also going to have the larger battery.
    Sure it uses a lot of plastic, but don't underestimate plastic.

    The only reason why the A6 did so well in Geekbench is because it owned in the memory tests. As far as CPU tests, 33% slower than the Tegra 3. Sure, it is Quad, but Cortex-A9 quad. We all know already in benchmarks that the S4 in Multithreading is still usually faster than Tegra 3. That is what makes me iffy about this Geekbench.
    Plus for phones, I'm more interested in single threaded performance, and the A6 should still own a Tegra 3 in single threaded tests easily.
  • sansh1r0 - Monday, September 17, 2012 - link

    "You have to remember that the iPhone 5 is the thinnest smartphone in the world, and way lighter than most Android phones."

    Both the Huawei Ascend P1 and the Oppo Finder are thinner than the iPhone 5.


    Apple lied in their presentation and the media and readers didn't care to get facts straight.
  • PeteH - Monday, September 17, 2012 - link

    According to that first link, the Huawei Ascend P1 is 7.7mm thick, which is not only thicker than the iPhone 5 (7.6mm), but also significantly thicker than advertised (6.68mm).

    I dug around a little, and from the photos I found it of both phones it looks like they have "bulges" either at the top or bottom of the device. I'm betting both companies are defining the overall device thickness as the average thickness of the entire device.

    Does anyone happen to know the worst-case thickness of those devices? I wouldn't be surprised if the iPhone 5 is actually the thinnest smartphone when measuring worst-case thickness, while these phones are both thinner when measuring average thickness. In other words nobody lied, they just used different definitions of thickness.

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