Analyzing the iPhone 5 Geekbench Resultsby Anand Lal Shimpi on September 16, 2012 8:31 PM EST
- Posted in
- iPhone 5
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:
|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|
|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:
|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|
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.
|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|
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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softdrinkviking - Sunday, September 16, 2012 - linkI wonder if apple is risking backing themselves into a corner by tailoring their hardware so closely to the device. There are all kinds of supply problems that could come up, and, well, it's happened in the past. IBM OS2 died because it didn't support enough peripherals. Obviously, it's not exactly the same, but I think I like the idea of multiple hardware vendors interacting with multiple platform/OS builders.
mavere - Sunday, September 16, 2012 - linkThey're still ARM licensees. If things go badly with their custom designs, they can always revert to generic A15 cores or something.
MadMan007 - Sunday, September 16, 2012 - linkI think the screen is supply-limited and that contributed to the pre-order sellout. Of course Apple didn't spin it that way, but if demand really was that much higher than anticipated they did a very poor job of production planning. I don't know why people don't realize that a product selling out when there is still demand is actually a failure by a company.
aribencannan - Sunday, September 16, 2012 - linkit may not necessarily mean failure by the company. 4S was available too much too soon (from Apple's point of view). Queues in form of apple stores were short or non-existent. Considering this in the light of every previous iPhone released, this gave the impression that the demand for 4S was not on par with previous phones. This may very well be a marketing strategy to create demand for the phone by word-of-mouth advertising during the initial period.
Sunrise089 - Sunday, September 16, 2012 - linkI'm sorry, but this simply isn't the way it works with tech products people purchase infrequently and at non-random time points.
If beer sells out at the local supermarket or in a whole region someone probably did a bad job (forgetting about the Super Bowl, etc).
New phone releases aren't like that. Lots of customers want the buy the product immediately, such that total lifetime sales are HEAVILY front-loaded. In order to meet all that demand on day 1 you would need either:
1) Massive production capacity that would run under capacity for 75+% of the product's life cycle.
2) Lower production levels that start very early, such that a huge number of phones are available by release.
Option 1 isn't cost effective, and option 2 means you're late to market and EVERYONE has to wait for the device rather than SOME people.
The real solution, if you don't like queuing (which essentially makes people pay a 'waiting in line' cost to decide who gets a phone right away) is simply to charge a higher price at first and lower it dynamically as demand falls. That's considered unacceptable for various business reasons I don't pretend to be an expert on, but it's clearly not something any of the major players are willing to do.
Given that, long lines and shortages at launch that then clear up are pretty much the ideal solution.
iwod - Sunday, September 16, 2012 - linkHow is that risking it when the SoC will be produced by Samsung whether it was apple designed or not?
And the only ones that could afford to design their SoC for two different Fabs, Samsung or TSMC will only be Apple or Qualcomm. Other dont have the volume to afford it.
Monkeysweat - Monday, September 17, 2012 - linkI also don't think OS2 sold 2 million devices in one weekend.
With the volume that Apple ships, they are not backing themselves into any corner, they are the designer from what you see and interact with all the way down to the corner, even if they don't manufacture 100% of it, they at least control every aspect. Not many companies can do this.
The tailored designs will be what they want so there is as little waste as possible in size or battery drain,,, if a SoC has even a couple features Apple won't use, they are taking up space and possibly some battery drain.
vol7ron - Monday, September 17, 2012 - linkwho said OS2 died?
Yorgos - Sunday, September 16, 2012 - linkHow about getting a comparison chart with other high-end smartphones?
dagamer34 - Sunday, September 16, 2012 - linkWe will probably have to wait for the full review in 2-3 weeks.