Performance

When the 4 was announced, my curiosity (and perhaps yours as well?) was about the flavor of Apple’s A4 SoC inside the phone. The rumor was that the A4 in the iPhone 4 had a full 512MB of memory, compared to 256MB in the iPad’s A4. iFixit took an iPhone 4 apart (with relative ease I might add) and confirmed the presence of 512MB. Look at the A4 in this picture, the Samsung part number on the right edge of the chip starts out K4X4G. The K4X denotes a Samsung mobile DRAM and the 4G refers to its density: 4Gbit or 512MB.

More memory should mean a smoother multitasking experience on the iPhone 4. Remember that iOS 4 keeps all fast task switching enabled apps resident in memory even after you’ve switched away from them. They are only kicked out of memory if you run low or if you force quit them. With more memory you should be able to keep more apps in memory without unwillingly forcing them out. The 512MB of RAM should also give the OS more breathing room in lighter multitasking scenarios, a problem many are already seeing on the iPhone 3GS running iOS 4. In practice the 4 is smoother when running iOS 4. There are still some hiccups but not as bad as on the 3GS, and definitely not as bad as on the 3G. The OS was clearly designed with the iPhone 4 as the performance target.

The big question that remains is what clock speed the iPhone 4’s A4 is running at. The assumption was 1GHz however Apple was very careful not to mention clock speed, unlike at the iPad launch. Saying nothing usually means there’s nothing good to say.

I ran a whole bunch of benchmarks on the iPhone 4 and the iPhone 3GS running iOS 4 to try and figure out what CPU speed we might be dealing with. The early reviews imply that the A4 in the iPhone 4 is running at a speed greater than the 3GS’s 600MHz, but slower than the iPad’s 1GHz. Let’s try and find out what it’s really running at.

We’ll start with the real world tests, first SunSpider. A javascript performance test this benchmark is completely network independent but it measures the performance of the browser as well as the underlying hardware. It is small enough to make memory size differences negligible so between the two iPhones we should be seeing a pure CPU comparison:

The iPhone 4 manages a time that’s 25% faster. Note that this test is just as much about the software stack as it is about CPU/platform performance. The Froyo update makes the Nexus One ridiculously fast in this benchmark. It just shows you how much room there is to improve performance on these Android handsets. The next leapfrog is going to be once the entire Android world moves to 2.2.

Next up is the Rightware BrowserMark. This test combines JavaScript and HTML rendering performance:

BrowserMark spits out an overall score but with no indication of what the score actually means. In this case we’re looking at 18.4% better performance than the iPhone 3GS. The iPad is 34% faster than the 4, which supports the theory of the A4 running at ~750MHz in the new iPhone.

There's also the possibility that the A4 CPU clock varies depending on load and other factors but the run to run consistency in all of our tests seems to indicate otherwise. We also can't ignore the fact that the iPad and iPhone now run vastly different OS revisions. In some cases iOS 4 actually takes a step back in performance compared to iOS 3.2. That undoubtedly makes the iPad vs. iPhone 4 comparison about much more than CPU performance.

Froyo's improved Javascript performance sends the Nexus One nearly to the top of the list here, only bested by the iPad. While Apple has definitely improved performance with the iPhone 4, it seems that it will only take a software update for Android phones to surpass it.

To measure web browsing performance I downloaded a bunch of different web pages and saved as much of them as possible locally on a server. I used WiFi on all of the devices to connect to my local server and timed average load time. I repeated the test at least 3 times and threw out any unusually high or low numbers. Performance was from a clean restart with no additional programs running in memory.

Note that these numbers aren't comparable to other reviews as we've updated software versions on two of the phones. The iPhone 3GS is now running iOS 4 which resulted in some numbers going up while others went down. And the Google Nexus One is running the officially released build of Android 2.2, codenamed Froyo.

What these tests should show is the overall performance of the platform when all network bottlenecks are removed. Obviously hiding in a tunnel under a lead umbrella will make any phone slow, but we’re looking at peak performance here.

The first test is the new AnandTech front page. Here we’ve got tons of images and HTML, meaning we’re stressing both bandwidth and code parsing speed.

The iPhone 4 is no faster than the 3GS (actually slightly slower, but we'll chalk that up to timing variance) here. The Froyo update to the Nexus One makes it lightning quick, almost as fast as the iPad in our first test.

Next up we have the first page of our recent Zotac XBOX HD-ID11 review. The balance shifts from tons of images to more HTML processing:

Here we see more of what I expected: the iPhone 4 is around 25% faster than the 3GS running iOS 4. Android 2.2 running on the Nexus One is basically as fast as the 4.

Using our Print this Review function, this next test loads our entire 2010 15-inch Macbook Pro review. While the other two tests had some flash ad content, this one is completely devoid of it so the HTC phones shouldn’t be penalized:

Here the iPhone 4 is 11% faster than the 3GS and about the speed of the iPad. There are other bottlenecks at play here so we don't get further performance scaling. The Froyo update helps the Nexus One a bit but the iOS devices are still quicker.

Our most intensive test is up next with a load of the Engadget front page:

The Nexus One is ahead of the 4 once more with its Froyo update. And the iPhone 4 is 34% faster than the 3GS.

Our most CPU bound test is up next. I put together a custom page with a ton of tabular content and a single page copy of our 15-inch MBP review to make the load take some time at least.

Surprisingly enough there's no difference between the 3GS and the 4 here, perhaps my test is less CPU bound than I thought. Froyo improves the Nexus One's performance a little bit.

Low Level Synthetic Tests

If we assume that we’re mostly CPU bound in all of these cases (a fair assumption given how fast Atom can run through all of these tests), then we’d be looking at a ~750MHz clock speed for the iPhone 4’s A4 assuming no other architectural changes. That’s actually a pretty big assumption. The A4 is widely believed to be a 45nm SoC using an ARM Cortex A8. At 45nm there should be room for a larger L2 cache than what was used in the iPhone 3GS’s SoC.

Perhaps some more synthetic tests will help us figure out what’s going on. I turned to Geekbench, now available in an iOS version.

Geekbench spit out a number of overall results that gave me a good enough summary of what’s going on to make an educated guess:

The CPU specific tests all indicate the iPhone 4 is around 25% faster than the iPhone 3GS. That would imply at least a 750MHz clock speed if all else is the same. Assuming we don’t get perfect CPU scaling with all of these tests, I’d venture a guess that 800MHz is more accurate. If the A4 does indeed have larger caches however, Apple could get away with a lower clock speed.

The memory results are particularly telling as they all scale very well going to the iPhone 4, better than the CPU results in fact. This could lend credibility to the theory of larger internal caches or perhaps to an improved (faster) memory subsystem.

Unfortunately until we get the iPad on iOS 4 we can't get a better idea of CPU scaling. I'm not even sure how reliable that will be at this point. If Apple was willing to change the amount of memory the A4 package housed between the iPad and iPhone 4, who is to say that it wouldn't have a slightly different design for the iPhone 4 (e.g. larger caches). The designs may not be physically different but we may instead be looking at binning. Given Apple's unwillingness to talk about the architecture here I think the safest bet is that we're looking at an 800MHz ARM Cortex A8 core in the iPhone 4 and a 1GHz core in the iPad.

Why the lower clock? It's all about battery life.

Speakerphone Volume Incredible Battery Life
POST A COMMENT

269 Comments

View All Comments

  • bplewis24 - Monday, July 12, 2010 - link

    Consumer Reports confirms what I have commented on earlier about this article: that the "best case scenario" testing of one phone is clearly an attempt to excuse away this clear design flaw in a biased review. See the article here: http://blogs.consumerreports.org/electronics/2010/... .

    And watch the video. This testing was done in a controlled environment with an RF Isolation Chamber that is impervious to outside radio signals. I suggest you guys stop misleading the tech nerd population with this review now, and revise it.

    Brandon
    Reply
  • plastic_avatar - Monday, July 12, 2010 - link

    How can you not respect the research of someone who slides in an apt geek reference? Reply
  • zholy - Tuesday, July 13, 2010 - link

    Only Apple can release a product with such a design flaw and respond to complaints with either "you're holding it wrong" or "buy another product to make it work correctly". Any other company would have their product returned in droves, Mac fanatics just say "ok" Reply
  • Hengie2000 - Saturday, July 17, 2010 - link

    Help! I am a wireless tech that uses field test daily to survey in building wireless projects, but the iphone 4 or 4.0 upgrade lost that capability. I am willing to pay for someone to make a field test app or follow the steps that Brian and Anand have listed in this story. Is there any way to reach these guys for more details to get field test running on the iphone4? Does this give full field test menus or only replaces the signal bars with decibels? Reply
  • Stang289 - Monday, July 26, 2010 - link

    It would be great if you had Palm Pre Plus and Pixi Plus performance numbers included in smartphone reviews. I would like to see how they stack up against other smartphones. Reply
  • marxster - Thursday, September 9, 2010 - link

    ...after all that, I'll give you my real world experience. We have a 3Gs and a 4 in our household. The 3Gs always shows more bars and does not drop calls at all while my iPhone 4 does drop calls and has less bars.

    We live far away from the closest tower and the iphone 4 doesn't ever get better reception here than -103db.

    I'm now afraid to receive calls because I know they'll be dropped. Makes my phone useless.

    I should say that both phones are on the latest iOS version and there isn't much of a difference whether I use a case or not.

    By the way, please explain this to me. Why did Apple bother to spend millions of dollars shipping out cases when they clearly don't get rid of the problem. When I cup my phone with the case on, the bars drop just the same as without.
    Reply
  • MisterQED - Wednesday, October 20, 2010 - link

    I am not a member of the “tin foil hat” crowd, I’m a guy with a physics degree and a Ham license, so I know a bit about radios. What I am about to point out seems so obvious to me, but I have never heard it discussed anywhere. Your article discusses the effects of having a exposed antenna as it effects phone reception, but that misses the main point, this is a receiving and transmitting antenna. Having skin contact with a transmitting antenna is not safe. Allow me to explain my thought process and tell me if I have a flaw in my logic.

    1) Constant irritation causes cancer. Whether it is fiberglass fibers, silica dust or coal dust in our lungs, to UV radiation from skin exposed to the sun, if you irritate an area consistently for long periods of time, you are just asking for cancer.

    2) RF radiation from most phones is a subject of worry and present discussion, but it doesn’t worry me. RF radiation is a worry because it will cause electrical conduction thru body tissue. This would be an irritation and consistent irritation can lead to cancer. RF radiation from most phones has two methods of conduction, capacitive and inductive.

    a) Capacitive needs: a sizable area, small dielectric distances and high frequencies. Cell phones have the high frequencies, but all other designs keep minimal gaps between antennas and the operator’s skin. Also the operator’s finger tips provide a rather small area to support capacitive conductance.

    b) Inductive conduction needs frequency matched radiators to allow conduction i.e. a good antenna on each end. Body parts make poor antennas, and bodily dimensions generally don’t match the proportions of ideal radiators, so inductive conduction isn’t really a worry.

    3) iPhone 4s, unlike any previous device, allow a third and a magnitude more effective connection between an operator and a transmitting antenna, a resistive connection. All a resistive connection needs is a low resistance, which skin has when sweaty or damp and the antenna has if it is not covered by a non-conductive coating. To add insult to injury, this contact de-tunes the antenna making it less efficient. This inefficiency causes the transmitter to up the power output as cell phones work on a “yell loud enough to be heard” system, so the worse the reception the more power the phone will pump into the antenna to be able to communicate with the cell tower.

    So unless you can show me where my logic has lead me astray, I would expect that in the future some percentage of the population that use an iPhone without a case may find a small possibly cancerous mole forming on one of their fingertips.

    That is a bigger problem than some dropped calls, so why didn’t you mention it.
    Reply
  • smithpercy - Sunday, November 14, 2010 - link

    Does this mean that I could cold weld a suitable socket to the gsm antenna side strip to allow a patch cable to an external antenna and get reception in the very marginal areas that I spend most of my time in?? I know that the shield would have to be grounded but that could be done thru one of the other connectors. I understand that would void the warranty, and give apple a conniption fit but that is their problem. Reply
  • keri - Thursday, February 24, 2011 - link

    serious question here. Reply

Log in

Don't have an account? Sign up now