Understanding the iPhone 3GS
by Anand Lal Shimpi on July 7, 2009 12:00 AM EST- Posted in
- Smartphones
- Mobile
Putting it in Perspective
Below is a table of the CPUs used in some of the top smartphones on the market, let’s put our newly refreshed knowledge to the test.
| CPU | Issue Width | Basic Pipeline | Clock Speed | |
| Apple iPhone/iPhone 3G | Samsung ARM11 | single | 8-stage | 412MHz |
| Apple iPhone 3GS | Samsung ARM Cortex A8 | dual | 13-stage | 600MHz |
| HTC Hero | Qualcomm ARM11 | single | 8-stage | 528MHz |
| Nokia N97 | ARM11 | single | 8-stage | 424MHz |
| Palm Pre | TI ARM Cortex A8 | dual | 13-stage | 600MHz |
| RIM Blackberry Storm | Marvell ARM11 | single | 8-stage | 624MHz |
| T-Mobile G1 | ARM11 | single | 8-stage | 528MHz |
The first thing you’ll notice is that there are a number of manufacturers of the same CPUs. Unlike the desktop x86 CPU market, there are a multitude of players in the ARM space. In fact, ARM doesn’t manufacture any processors - it simply designs them. The designs are then licensed to companies like Marvell, Samsung, Texas Instruments and Qualcomm. Each individual company takes the ARM core they’ve licensed and surrounds it with other processors (e.g. graphics cores from PowerVR) and delivers the entire solution as a single chip called a System on a Chip (SoC). You get a CPU, GPU, cellular modem and even memory all on a single chip, all with minimal design effort.
A derivative of this is what you'll find in the iPhone 3GS
While it takes ARM a few years to completely architect a new design, their licensees can avoid the painful duty of designing a new chip and just license the core directly from ARM. ARM doesn’t have to worry about manufacturing and its licensees don’t have to focus on building world class microprocessor design teams. It’s a win-win situation for this business.
For the most part, ARM’s licensees don’t modify the design much at all. There are a few exceptions (e.g. Qualcomm’s Snapdragon Cortex A8), but usually the only things that will differ between chips are clock speeds and cache sizes.
The fundamentals of the architectures don’t vary from SoC to SoC, what does change are the clock speeds. Manufacturers with larger batteries and handsets can opt for higher clock speeds, while others will want to ship at lower frequencies. The ARM11 based products all fall within the 400 - 528MHz range. These are all single-issue chips with an 8-stage pipeline.
| iPhone 3G (ARM11) | iPhone 3GS (ARM Cortex A8) | |
| Manufacturing Process | 90nm | 65nm |
| Architecture | In-Order | In-Order |
| Issue Width | 1-issue | 2-issue |
| Pipeline Depth | 8-stage | 13-stage |
| Clock Speed | 412MHz | 600MHz |
| L1 Cache Size | 16KB I-Cache + 16KB D-Cache | 32KB I-Cache + 32KB D-Cache |
| L2 Cache Size | N/A | 256KB |
The iPhone 3GS and the Palm Pre both ship with a Cortex A8. I’m actually guessing at the clock speeds here, there’s a chance that both of these devices run at closer to 500MHz but it’s tough to tell without querying the hardware at a lower level. The Cortex A8 gives us a deeper pipeline, and thus higher clock speeds, as well as a dual issue front end. The end result is significantly higher performance. Apple promised > 2x performance improvements from the iPhone 3GS over the iPhone 3G, such an increase was only possible with a brand new architecture.
I must stress this again: clock speed alone doesn’t determine the performance of a processor. Gizmodo’s recent N97 review complained about the speed of Nokia’s 424MHz processor (rightfully so). The review continued by saying that HTC uses 528MHz processors, implying that Nokia should do the same. The second part isn’t what Nokia should be doing on its $500+ smartphone, what is inexcusable is the fact that Nokia is not using ARM’s latest and greatest Cortex A8 on such an expensive phone. It’s the equivalent of Dell shipping a high end PC with a Core 2 Duo instead of a Core i7; after a certain price point, the i7 is just expected.
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Affectionate-Bed-980 - Wednesday, July 8, 2009 - link
It's unacceptable because what? HTC Touch Diamond 2 and Touch Pro 2 are flagship phones with ARM11 processors? Yes I pointed out some phones that have it, but have you guys even seriously used an S60 phone? Multiple S60 phones? I've gone through N80, N95, N82, and I've toyed with an N85 and 5800 also. The N97 is certainly fine in usability. It could use some more RAM, but even if you stuffed a Cortex A8 and some more RAM, the phone is still going to get a lot of flak except for people who look at it on paper. Symbian S60v5 is perfectly fine on ARM11. It doesn't need some insane CPU to keep up with the UI.Moreover, the N97 isn't really that much of a gaming platform like the iPhone. Think of the N97 like the Touch Pro 2. The Touch Pro 2 is more business oriented with the QWERTY and everything. HTC didn't upgrade the camera, and didn't bother to build it the same way the flagship Diamond 2 was built. This doesn't mean it's a BAD phone.
You guys are thinking of this whole thing like a computer or something. Have you seen the N95 photos? It's a 2007 phone. Pretty much the best 5MP all around. The N97 does a little better. Yes it demolishes the 3MP crap on the 3GS. So coming from a more computer-centric crowd here yes it makes sense to bash a CPU, but from a mobile phone perspective it's not even that bad at all. If anything the phone was first a phone before it was a camera and then an MP3 player, and now a powerhouse mini computer. If you're telling me that in 2006 I could've bought a Sony Ericsson 3 MP cameraphone, then why are we still stuck there on the 3GS? There are more important features that phones push for such as music, camera, later GPS and connectivity, and now processing power. Give it some time and I bet you Nokia will have a winner soon.
What crappy screen on the N97? Resistive? Get over it. The iPhone is capacitive, so all phones must be capacitive? The iPhone has a Cortex A8, everything else must have it? Please. Multi touch is patented by Apple, so it's a little difficult to move into that arena for now. There are advantages and disadvantages to both resistive and capacitive screens. Just because the N97 doesn't mimick the iPhone doesn't mean it sucks. HTC's WinMo phones are resistive screens too. So are the new Samsung Omnia II and Pro phones. So is the new Sony Ericsson Satio.
Different phones are built differently, but honestly when you look at pure functionality, the lack of multitasking is much larger than a CPU difference.
I feel it is justified to say Nokia needs to get to work, but to hear this from people who really doesn't have as much experience with unlocked phones is like hearing one of those ditzy people who buys Apple thinking it'll solve their spyware problems on their PC tell you why a Mac is superior. I'd rather hear it from the computer guru. Gizmodo may be negative, but I think Engadget gave the N97 a fair look and so did other reviewers like PhoneArena, GSMArena, Mobile-Burn, Symbian-Guru.
Look I have nothing against Apple. I have a 3GS too. It's just not my thing and I'm back on my N-series. I'm not a Nokia fanboy or anything. There's plenty of criticism I've given the N97 and Nokia in the S60 section of HoFo, but I believe having had 3 iPhones, Anand is quite biased.
vshah - Wednesday, July 8, 2009 - link
Anand,Thanks for this excellent article, I really enjoyed the cpu benchmark/comparisons you did; they paint a very clear picture.
I was curious as to your thoughts on the multitasking implementation on Android. Holding down home for a couple seconds brings up the 6 most recently accessed apps/tasks, and I've always found switching between them to be pretty fluid. Have you had a chance to try that out?
Thanks,
Vivan
MrX8503 - Wednesday, July 8, 2009 - link
This isn't even a phone site and it has the most in depth review of the iphone yet.I guess being a tech site, Anandtech has an edge over other sites that just review phones.
Good Work!
kmmatney - Wednesday, July 8, 2009 - link
I needed a new phone for work, and spent about 30 minutes in the local AT&T store testing out phones yesterday. After using the blackberry and iPhone for quite some time, I have to say the iPhone was much better. I was way more productive with it - everything was easy to do, while I felt like all the other phones were fighting me. Overall, a fantastic phone for business - I went for the 16GB 3GS model - the only gripe is the 7 day wait for shipment.sprockkets - Wednesday, July 8, 2009 - link
You mentioned using voice command. Can you use it via a BT headset?Also, does it play ringtones over the headset? Does it announce who is calling over the headset?
nafhan - Wednesday, July 8, 2009 - link
Thanks for a great article!One minor complaint, and it's really not even a complaint. I want to point out that this would have made two excellent stand alone articles.
First article would have been about the current state of mobile CPU and GPU architecture. This section was excellent and detailed enough that I really felt it deserved it's own article rather than being lumped in as part of your iPhone impressions.
Second article would have been your impressions and review of the 3GS.
WeaselITB - Wednesday, July 8, 2009 - link
I agree with this - it does seem that there are two articles vying for attention here, and with a bit more polish they could have been published separately.That said, I do want to commend you for this article. These are the types of in-depth reports that made me start reading AT ten or so years ago, and they are the type of in-depth reports that keep me reading. Thanks, Anand.
Rolphus - Wednesday, July 8, 2009 - link
I think this is an important point. Apple see the iPhone as a device, exactly the same as the iPod. No "user" compares about the iPod's CPU, any more than they care about the CPU of their refrigerator. For it to be a true consumer device (rather than a computer), it should "just work", and work with acceptable performance, in all the situations it's designed for.Yes, us techies want to know more, and that's precisely why we come to sites like Anandtech and read your articles. I don't think the mainstream user is ever going to care about these specs, but rather what the phone can do.
medi01 - Wednesday, July 8, 2009 - link
Wouldn't it be better to review alternatives? Like Samsung's new shiny MOLED display smartphone?wuyanxu - Wednesday, July 8, 2009 - link
superb article! a lot more indepth than all other websites. would love to see more like this, with more information on how the graphics cores improved its performance.however, what you should not forget is avaliability of jailbreak for 3GS. in the conclusion you've mentioned the hassle of re-launching apps. with a jailbreak, you will be able to send an app to background and get instant re-lanuch.
my dream phone would be an iPhone with Andriod-like pull-down status bar notification system, and have JB's backgrounder come as standard.
the pull down status bar will have the top 2/3 to be notifications. press to launch its apps. the bottom 1/3 will be icons of opened apps, and to close it, simply drag the icon to a reserved area.
the idea is similar to a jailbroken app called mQuickDo, except with the notification system.