Apple iPhone 4S: Thoroughly Reviewed
by Anand Lal Shimpi & Brian Klug on October 31, 2011 7:45 PM EST- Posted in
- Smartphones
- Apple
- Mobile
- iPhone
- iPhone 4S
The A5 Architecture & CPU Performance
The original iPhone debuted with a single 412MHz ARM11 core built on a 90nm process. The 3G improved network performance in 2008 but left the SoC untouched. It wasn't until the iPhone 3GS in 2009 that the SoC got a major performance and power update. Apple moved to a 65nm process node, a brand new ARM Cortex A8 based SoC and an upgraded GPU. The A4 released in 2010 once again gave us a process shrink but kept the architecture unchanged.
Apple's A5 SoC
Apple's A5, first introduced with the iPad 2, keeps process technology the same while introducing a brand new CPU and GPU. The A5 integrates two ARM Cortex A9 cores onto a single die. The improvement over the A4 is tremendous. At the single core level, Apple shortened the integer pipeline without reducing clock speed. With a shorter pipeline the A5 gets more done per clock, and without decreasing clock speed the A5 inherently achieves better performance at the same clock. The move to the Cortex A9 also enables out-of-order instruction execution, further improving architectural efficiency. I've heard there's a 20% increase in performance per clock vs. the Cortex A8, but combine that with the fact that you get two A9s vs a single A8 in last year's design and you get a pretty big performance increase.
There are several situations where the A5's two cores deliver a tangible performance benefit over the A4's single core. Like Android, iOS appears to be pretty well threaded. Individual apps and tasks can take advantage of the second core without a recompile or version update. The most obvious example is web browsing.
Mobile Safari is well threaded. Javascript rendering can be parallelized as well as parts of the HTML parsing/rendering process. All of the major Javascript performance benchmarks show a 60 - 70% increase in performance over the A4, which is partially due to the availability of the second core:
This translates directly into faster page load times. As you can see in the video below, the iPhone 4S (left) loads the AnandTech front page over WiFi in about 5 seconds compared to 9 seconds on the iPhone 4 (right). That's really the best case scenario, the improvement in the next page load time was only about a second (7s vs 8s).
Typical improvements in load time fall in the 10 - 70% range, contributing significantly to the phone feeling snappier than its predecessor. To quantify the improvement I ran through our standard web page loading suite, a test that hits AnandTech, CNN, NYTimes, Engadget, Amazon, Digg and Reddit hosted locally on our lab's network. The average page load time over WiFi for all of the pages is below:
While web page rendering is a natural fit for multiple cores, I was surprised by how poorly threaded some apps ended up being. For example, although I did see performance improvements in exporting edited videos from the iOS version of iMovie, the gains weren't always evident. A quick profile of the app revealed that much of the export process is still single threaded. Just as we've seen on the desktop, there will be some added work necessary to get all apps to utilize multiple cores on iOS.
It's not always performance within an app that saw improvement with the A5: application install and launch times are also much quicker on the 4S. The time to launch Epic's iOS Citadel demo went from 32 seconds on the iPhone 4 to 22 seconds on the 4S. While the iPhone 4 may feel fast enough for many users, the 4S is noticeably faster.
Much of the faster feel comes from by shaving off of seconds here or there. For example, I noticed apps like Messages pop up just slightly quicker on the 4S and you'll see your listing of messages a hair faster than you would on the 4. In the video above you get a brief idea of the sort of subtle improvements I'm talking about. YouTube launches a fraction of a second quicker on the 4S vs the 4.
These subtle decreases in response time are simply icing on the cake. The move from a 4 to a 4S is one of those upgrades that you'll notice right off the bat but will really appreciate if you go back to an iPhone 4 and try to use it. If you do a lot of web browsing on your phone, you'll appreciate the 4S.
I wasn't entirely sure whether or not I could attribute all of these performance improvements to the faster CPU. It's possible that some of the tests I mentioned are IO bound and Apple could have used faster NAND in the 4S. To find out I rounded up a bunch of iPhone 4Ses at all available capacities and measured sequential write speed:
Apple uses multiple sources for NAND so it's possible that you'll see these numbers move around a bit depending on your particular phone. It looks like the iPhone 4S' NAND is no faster than what Apple shipped last year - at least in sequential write speed. The target appears to be 20MB/s and Apple does its best to stay around there. My iPhone 4 is actually pretty quick at 22MB/s but the advantage isn't significant enough to make a huge deal about. I don't have a good way of measuring random IO performance yet but application launch time is largely governed by sequential IO so I don't expect we're seeing gains from anything outside of the CPU and memory bandwidth in the earlier tests.
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Formul - Monday, October 31, 2011 - link
There is about a dozen fairly similar android phones every month. As iPhone gets refreshed just once every year (this time year and a half) and has bigger market than any single android phone out there it makes sense to make the review thorough. I guess Nexus Prime and even Razer will get similar lengthy reviewsa ... as did many other android phones before that (galaxy s2 for example had about the same as this one).You are the one biased here. Counting the number of android articles on any gadget blog will seriously outpace the iPhone by far. You should shut up and read what you want, no one is forcing you to read this blog or any particular article on it. I dont read android articles, i dont care about android all that much. Why do you have to troll here if it does not interest you after all?
Anand Lal Shimpi - Monday, October 31, 2011 - link
I believe we did just that for the Galaxy S 2 review:http://www.anandtech.com/show/4686/samsung-galaxy-...
We don't have the RAZR, Galaxy Nexus or S2 Skyrocket, but we typically do a deep dive whenever there's a new platform transition or something truly unique to look at.
Take care,
Anand
LordSojar - Tuesday, November 1, 2011 - link
Hmm, touche Anand, I had forgotten about how detailed the S2 review was.The RAZR doesn't warrant a particularly detailed review I suppose, but I think the S2 Skyrocket might warrant a detailed antenna review etc considering the transition to LTE along with, what should be a major change to the antenna and should (I think) have QC's MDM9615 or MDM8215 chips in it... which is a big deal considering those could yield not only significant speed gains along with an antenna update, but some major throughput.
Cheers
doobydoo - Tuesday, November 1, 2011 - link
'Samsung releases a new phone that has overall better features, faster CPU, faster NAND, a different and arguably better (or at least equal) screen'I hope you are comparing to the OLD Samsung, in this sentence, rather than comparing to the iPhone 4S.
The CPU/GPU performance of the iPhone 4S is not comparable to the Galaxy S2, and I would argue the features are very much superior too.
Which, incidentally, along with the dual-antenna design, Siri, brand new camera, makes the iPhone 4S much more of a step up than the Samsung Galaxy to Samsung Galaxy S2. (The Galaxy S was about the same performance as the iPhone 4. The Galaxy S2 is slower than the iPhone 4S, therefore iPhone 4S is a bigger upgrade).
And of course, as Anand said, they thoroughly review most phones, and as the other poster says, the Android phones come out way more often so over the same length of time they get at least as much if not more coverage.
Tetracycloide - Tuesday, November 1, 2011 - link
The Galaxy S2 released in May. The 4S released in October. The next Galaxy phone, the generation the 4S is actually going to compete with, is the Galaxy Nexus. What I'm saying is your point would hold more water (or any at all) if Samsung didn't make 2 upgrades in the space of time it took Apple to do 1 so the differential between generations is hardly an apples to apples comparison (pun intended).thunng8 - Tuesday, November 1, 2011 - link
But the Galaxy Nexus isn't any faster than the S2. The main benefit is the new operating system and higher resolution screen.The Nexus is actually a significant step backwards from the S2 in terms of camera (likely from the samples on the prototype) and GPU (definitely since it is using the SGX540) performance
doobydoo - Wednesday, November 2, 2011 - link
Release dates will not stop phone users comparing the iPhone 4S to the Androids released in March 2012, just like they compared all the Androids over the last 17 months to the iPhone 4.The iPhone 4S, right now, is competing with the Galaxy S2 directly.
The Nexus Prime, as the other comment alluded to, is a significant downgrade from the Samsung Galaxy S2. Indeed, it uses the same GPU as used in the much older Samsung Galaxy S (albeit clocked higher).
The Galaxy S to S2 took approximately a year inbetween generations (June 2010 to May 2011), which is very much in line with the typical Apple release cycle of annually (this year was the exception). Even this year, with the extended timeline between iPhone 4 and 4S, Samsung didn't make 2 upgrades during that time. Your point would hold more water (or any at all) if it had.
Tetracycloide - Wednesday, November 2, 2011 - link
It's obvious you're not making a real comparison between current products but instead of admitting that you pretend it's a non-issue and then strangely fought that issue anyway by suggesting I'm not actually right to call you out on these shenanigans. So thanks for being obtuse about this, it makes it much easier to dismiss your position as that of an irrational fan-boy (at least it does when combined with the condescension in some of the other threads you've commented on here).doobydoo - Friday, December 2, 2011 - link
'It's obvious you're not making a real comparison between current products'Erm, huh?
That's EXACTLY what I'm doing.
What YOU'RE doing is asking is to compare a phone which isn't even out yet with a phone which is. You're trying to 'pretend it's a non-issue' that the phone you say the iPhone 4S should be compared with wasn't even out when this discussion started. THAT is the definition of fanboy-ism. It's like the constant like of Android fans 'x WILL be better when it eventually comes out' - and THAT is obtuse.
So, the only comments which can be dismissed are YOUR fanboy comments about 'x phone released in x months will be better'. Turns out you were wrong anyway, but that's irrelevant - the bottom line is you don't want iPhone to be compared to CURRENT Android phones, but instead compared to FUTURE ones.
Rational, much?
As it happens, it's out now, and isn't even much of an improvement on the Samsung Galaxy S2
Lucian Armasu - Wednesday, November 2, 2011 - link
The cameras seem to be about the same, according to Anand. I've actually found the SGS II camera to be a bit better in photo comparisons. Siri? I still think it's more of a gimmick for now. Maybe in 5-10 years it will be actually useful. Once the novelty expires, people will barely even use it in a few months. The same happened with FaceTime which everyone went crazy about at launch, and then they stopped using it completely.The CPU of the SGS2 IS faster than iPhone 4S CPU. There's no way Apple managed to get a 50% performance improvement for the same Cortex A9 chip that Samsung is using.
I think Anand can confirm this. He wasn't very clear in the review. He was only talking about the improvements it gets over the old Cortex A8.