The iPhone 6 Review
by Joshua Ho, Brandon Chester, Chris Heinonen & Ryan Smith on September 30, 2014 8:01 AM EST- Posted in
- Smartphones
- Apple
- Mobile
- iPhone 6
A8: Apple’s First 20nm SoC
As has been customary for every iPhone launch since the company began publicly naming their SoCs, Apple has once again rolled out a new SoC for their latest line of phones. With the launch of the iPhone 6 series Apple is now up to their eight generation SoC, the appropriately named A8.
After a period of rapid change with the A6 and A7 SoCs – which introduced Apple’s first custom CPU design (Swift) and the first ARMv8 AArch64 design (Cyclone) respectively – A8 is a more structured and straightforward evolution of Apple’s SoC designs. Which is not to say that Apple hasn’t been busy tweaking their designs to extract ever-improved performance and power efficiency, as we’ll see, but our examination of A8 has not uncovered the same kind of radical changes that defined A6 and A7.
The heart and soul of A8 is as always the CPU and GPU. We’ll be taking a look at each of these individually in a moment, but from a high level both of these are evolutions of their predecessors found in A7. Apple’s GPU of choice remains Imagination’s PowerVR, having upgraded from the Series6 based G6430 to Imagination’s newer GX6450 design. Meanwhile Apple continues to develop their own CPUs and A8 packs their latest design, which is an enhanced version of the Cyclone core first introduced in A7.
Stepping away from the GPU and CPU for the moment, the biggest change about A8 is that it’s smaller. As discovered by Chipworks, A8 is being fabricated on TSMC’s new 20nm process, making the iPhone 6 among the first smartphones to be shipped with a 20nm SoC.
This move to 20nm is not unexpected, but nonetheless it is considerable for a couple of reasons. The first is that this means Apple has moved production over to TSMC’s 20nm HKMG Planar process, making this the first time an Apple SoC has been manufactured anywhere but a Samsung fab. There are numerous possible reasons for this – and not every reason needs to be technical – but from a process development standpoint it’s important to note that over the last few generations TSMC has been the leader among contract foundries, being the first to get new processes up and running for volume production.
| Apple A8 vs A7 SoCs | ||||
| Apple A8 (2014) | Apple A7 (2013) | |||
| Manufacturing Process | TSMC 20nm HKMG | Samsung 28nm HKMG | ||
| Die Size | 89mm2 | 102mm2 | ||
| Transistor Count | ~2B | "Over 1B" | ||
| CPU | 2 x Apple Enhanced Cyclone ARMv8 64-bit cores |
2 x Apple Cyclone ARMv8 64-bit cores |
||
| GPU | IMG PowerVR GX6450 | IMG PowerVR G6430 | ||
This move is also quite considerable because it means for the first time Apple is manufacturing their SoCs on a bleeding edge manufacturing process. Prior to this Apple has been slow to utilize new manufacturing processes, only finally utilizing a 28nm process in late 2013 for A7 over a year after 28nm first became available. The fact that we are seeing a 20nm SoC from Apple at a time when almost everyone else is still on 28nm indicates just how much the market has shifted over the last few years, and how Apple’s SoC development is now synchronized with the very edge of semiconductor fabrication technology.
Finally, the switch to 20nm is interesting because after the last couple of generations being so-called “half node” jumps – 45nm to 40nm to 32nm to 28nm – the jump from 28nm to 20nm is a full node jump (note that Apple didn't ever use 40nm, however). This means we are seeing a larger increase in transistor density than in the previous generations, and ideally a larger decrease in power consumption as well.
In practice TSMC’s 20nm process is going to be a mixed bag; it can offer 30% higher speeds, 1.9x the density, or 25% less power consumption than their 28nm process, but not all three at once. In particular power consumption and speeds will be directly opposed, so any use of higher clock speeds will eat into power consumption improvements. This of course gets murkier once we’re comparing TSMC to Samsung, but the principle of clock speed/power tradeoffs remains the same regardless.
Not accounting for minor differences between TSMC and Samsung, in an ideal case Apple is looking at 51% area scaling (the same design on 20nm can be no smaller than 51% of the die area at 28nm). In reality, nothing ever scales perfectly so the density gains will depend on the kind of I/C being laid down (logic, SRAM, etc.). For the complete chip a 60-70% scaling factor is going to be a better approximation, which for Apple means they’ve picked up a lot room to spend on new functionality and reducing their overall die size.
| Apple SoC Evolution | |||||
| CPU Perf | GPU Perf | Die Size | Transistors | Process | |
| A5 | ~13x | ~20x | 122m2 | <1B | 45nm |
| A6 | ~26x | ~34x | 97mm2 | <1B | 32nm |
| A7 | 40x | 56x | 102mm2 | >1B | 28nm |
| A8 | 50x | 84x | 89mm2 | ~2B | 20nm |
Meanwhile once again this year Apple opened up on die size and transistor counts. A8 weighs in at around 2 billion transistors, as opposed to the “over 1 billion” transistors found on A7. We also have the die size for A8 – 89mm2 – which is some 13% smaller than A7’s 102mm2 die. This makes it clear that Apple has chosen to split their transistor density improvements between adding features/performance and reducing their size, rather than going all-in on either direction.
In the case of using a bleeding edge node this is generally a good call, as Apple and TSMC will need to deal with the fact that chip yields at 20nm will not be as good as they are on the highly mature 28nm process. With lower chip yields, a smaller die will offset some of those yield losses by reducing the number of manufacturing flaws any given die touches, improving the overall yield.
A8 With POP RAM Removed
Moving on, looking at A8 we can see that Apple’s memory subsystem design has not significantly changed from A7. Once again Apple has placed an SRAM cache on the chip to service both the CPU and the GPU. Based on an examination of the die and of latency numbers, this L3 SRAM cache remains unchanged from A7 at 4MB. Meanwhile we also find a series of SDRAM interfaces which drive the A8’s package-on-package (POP) based main memory. Based on teardowns from iFixit, Apple is using 1GB of LPDDR3-1600, the same speed grade of LPDDR3 and capacity that they used for the iPhone 5s. iFixit has found both Hynix and Elpida memory in their phones, so Apple is once again using multiple sources for their RAM.
When we start poking at memory bandwidth we find that memory bandwidths are consistently higher than on A7, but only ever so slightly. This points to Apple having worked out further optimizations to make better use of the memory bandwidth they have available, since as we’ve previously determined they’re still using LPDDR3-1600 speeds.
| Geekbench 3 Memory Bandwidth Comparison (1 thread) | ||||||
| Stream Copy | Stream Scale | Stream Add | Stream Triad | |||
| Apple A8 1.4GHz | 9.08 GB/s | 5.37 GB/s | 5.76 GB/s | 5.78 GB/s | ||
| Apple A7 1.3GHz | 8.34 GB/s | 5.21 GB/s | 5.67 GB/s | 5.69 GB/s | ||
| A8 Advantage | 9% | 3% | 2% | 2% | ||
The Stream Copy score ends up being the biggest gain at 9%. Otherwise the rest of the benchmarks only show 2-3% memory bandwidth increases.
More interesting is memory latency, which shows some unexpected improvements once we get out of the L1 and L2 caches. At both the 1MB – 4MB region of the SRAM and 6MB+ region of main memory, memory latency is consistently lower on A8 versus A7. In both cases we’re looking at latencies about 20ns faster than A7. This identical 20ns gain tells us that that Apple is still doing main memory lookups after the L3 lookup fails, and this in turn means the 20ns gain we’re seeing is due to L3 cache optimizations. We have a couple of ideas for how Apple could have improved L3 latency by nearly 20% like this, but at this time with Apple staying quiet on their architecture like usual, it’s not apparent which of these ideas are the correct ones.
Turning our eyes back to A8 one final time, we find that while a lot of die space is occupied by the CPU, GPU, and SRAM (as we’d expect), there is also quite a bit of space occupied by other blocks Apple has integrated into their design. Without already knowing what you’re looking for these blocks are difficult to identify, but even without being able to do this we have a reasonable idea of what blocks Apple has integrated. Among these we’ll find audio controllers, USB controllers, video encoders/decoders, flash memory controllers, the camera ISP, and of course all kinds of interconnect.
All of these blocks are fixed function hardware (or at best, limited flexibility DSPs), which are equally important to not only the A8’s functionality but power efficiency. By assigning tasks to dedicated hardware Apple does spend some die space on that hardware, but in return these blocks are more efficient than doing those tasks entirely in software. Hence Apple (and SoC designers in general) have a strong incentive to offload as much work as possible to keep power consumption in check. This move towards more fixed function hardware is part of a general “wheel of reincarnation” cycle that has been a constant in processor design over the years, which sees a continuous shift between fixed function and programmable hardware. SoCs, for the most part, are still going towards fixed function hardware, and this should continue for a while yet.
In any case, while we can’t identify individual blocks on A8 we do know that Apple has added a few features to A8 that are present in some form or another among these blocks. New to A8 is some mix of H.265 (HEVC) hardware, which would be necessary to enable the FaceTime over H.265 functionality that is being introduced on the iPhone 6. Apple’s “desktop class scaler” that is used for handling non-native resolution applications and for down-sampling the internal rendering resolution of the iPhone 6 Plus would also be present here.
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ninjaroll - Tuesday, September 30, 2014 - link
You have to tell yourself that not everyone commenting is around your age range. I feel like a lot of the haters are about 12-18 years of age. If they're older...well.. I feel bad for them.akdj - Saturday, October 4, 2014 - link
I think you nailed it ninjaThe 'age & ambiguity' question. As well as age, the differences between generations and what 'we‘ had available (I'm 44) when growing up vs the 'gen Y' mid 20s-mid 30s (I think the higher end still appreciates both or the 'big three' for what they are ..not crapping on what 'they're not'). Then weve got the 'kids'. I'd even go so far as to say 12-21/22 year olds. As the 22 year old SAW the impact the Iphone had in 2007, the 'actual' Android fight 'start' in 2008 at 15 & 16. They were graduating and going into college or vocational training when the iPad broke and the Xoom filled (tablet computing). They've seen in their 'formative' years the evolution of HiDPI displays and developed personal opinions about their extremely 'personal' devices (I've got teenagers! Yikes, believe you me when I say their 'personal' devices:))
Baby boomers, X & late Y didn't have cell phones growing up. Drug dealers and executives had pagers and computers were computers. They weren't 'connected' with the Internet (mainstream) and we paid a LOT of money for our Apple or Microsoft software and OS Updates. The incredible sea change Apple and Google have brought to the consumers and the masses regardless of income levels, location in the world and/or from developing countries ...they're penetration is significant. Obviously there are countries with their own restrictions, etc... But maybe they're the 'smart' ones for now...look at what the NSA/Patriot Act has done for the USA and her relationships even with our closest allies!
We're still at the infancy of 'mobile' comms/computers and connectivity. These iPhones ARE computers. The G3, Z3, S5 or 5s/6/6+!!! All of them. I think as we age, we remember. It's easier not to take for granted the way technology has empowered our lives, folded the world in half, and the incredible benefits and convenience we enjoy OR despise with 'cellular' phones, phabs n tabs! At times they feel more like a leash than freedom. When you're working and paying a mortgage or two, car payments and student loans (from two decades ago or current kids going into post Ed), groceries and 'energy' (from gasoline to heating gas, cooling electricity or your battery in your fell phone of choice), groceries and your kids' entry fees, new 'cleats' and mitts, pads and summer camps....THEN you'll get it. I'd bet dollars to donuts (such a dumbass saying, very unhip I know;))
As you age, technology will continue to evolve. Much of what we enjoy today is a direct and absolutely traceable line to developments during the 'Cold War'. Whether Russian or American, Chinese (anyone see their Olympics in Beijing? The opening and closing cereminies, etc? Kind of brings a new meaning to 'made in China' than it had when I was younger. IMHO they blew London completely outta the water ymmv as always)
Point being there isn't 35+ folks on this board waging this ridiculous Holy War between OEMs or OS's. There ARE paid folks from both sides as again, social media in the last decade (another 'new') has become JUST as important as their thirty and sixty second TV spots, sponsorships or product placement in movies! It's HUGE. & IMHO a VERY important and crucial element in a free internet society to have sites like Anand's ...that he's passed along to Brian and Ryan and the rest of the crew. I've been here for years and have ALWAYS found what I've come for. Objective measurements and subjective reviews. We're all human. If we're reviewing a product its in our nature to 'add' our opinions now and then
To me, as a user of OS X and Windows, UNIX, Android and iOS ...I feel like ANYone limiting themselves so blindly to what the 'enemy' is doing is ignorant, young and/or unemployed (if the latter, I feel for you if you're looking...but if you're lurking on forums like these zealots are they're NOT looking for employment. If you're out of work, you can spend 40-50 hours a week 'Looking' and in most developed nations...in other words ANYone that would criticize the other camp and not appreciate what they've already got)
At the end of the day, it Samsung making Apple work harder. Cupertino making MtView work harder and ALL of them starting to reap the awards Microsoft seemed to 'leak' off over the past 10-15 years. We're no longer in an X86, workstation at your desk on the 'intranet' to collaborate with a fax machine to send the final product. If you don't remember those days, it's tough to take these complaints seriously as my 5s and from the time I've spent with the 6/6+, my Air and retina mini all have a 'place' in my life. And every ONE of them is faster with quicker connectivity and MORE software available than at ANY point in my life and I'm only, hopefully half way to the finish line. As you age, you'll understand what I'm saying
That said ...If you're 44 & @ (mom's) home, in the basement, without a gig, and feeding your spiders backing these DBags arguing 'physical, objective, and factual' measurements of performance in the review....it's YOU that needs to reexamine your life and priorities.
Love is family, kids, coaching and watching them grow, through good times and bad. It's the iPhone, the S5 or Note 3 you're carrying that's capturing those memories. Ten years from NOW, there won't be a 'lightning' connector. An iPhone 6+ or Note7/G7 or Z8! USB will be dead and history is indicative of the evolving future, only us 'old folk' will be using Facebook ...but giving it our BEST shot to 'learn' to new and HIP MySpace, Netscape, AOL or today's Twitter and Facebooks
Remember kids, it's US, and my parents (your grandparents) that built this shit for you. Not YOU! You're reaping the benefits of the fruits of our labor. If you don't get out from behind the 600 dpi display you're so passionate about ...or get out of the house, learn how to ride a bike like Tony Hawk, snowboard like the 'Tomato' or innovate like Gates, Jobs and that snot nose kid from Stanford....young 'Zuke', you're futures are going to suck
Don't be a slave to your tools. Let them work for you, choose what best fits your idea and vision and occupation and you'll find out soon there's a helluva lot more to life than MHz, GB of RAM, and PPI determining what you can and can't see. As your ears fail you so, too, will your eyes and damned if I can't tell the difference between the '6' &6+, the new HTC or my Note 3/5s, Air or mini! All different, ALL a helluva lot better than my green/orange monochrome displays I was 'working' on in the early 90s, how incredible '16 color displays' were and the transition from cathode ray tube 'monitors' to LCD and LED/AMOLED/Plasma displays showed us the difference between our VHS tapes, 480p DVD collection and the BluRay, 1080p displays. Now packaging those pixels into the palm of your hand is absolutely, and genuinely AMAZING. Nothing short of true miracles in engineering
My dad graduated in 1972 with his bachelors in electrical engineering. Did it with a slide ruler and drafting kit he's still got today and the same kit myself and two of my three younger brothers took through engineering school with our TI calcs that did it all (early 90s), and my first 286 after my Apple IIe & IIc run. As a baby with the 8086 processor perhaps those of us born in the early to mid 70s and earlier are more 'appreciative' today than the younger generation. We're more patient, we've gained wisdom and most importantly we 'lived' without the Internet, with corded 'dial' phones (when I was a kid we had a party line...and only had to dial FOUR digits locally lol! Small town in northwest Montana). To me, I really HOPE there's youngsters as intrigued by ALL forms of operation systems and is the new 'Edison, Tesla, Carnegie or Jobs/Zuke/Gates' of a future era. Redesigning in his or her 13 year old mind an OS that's a 'learning OS'. Through the millions of lines of code to boot to the desk, half can be elimated as it learns YOUR usage and 'needs' ..that conforms to the individual and their needs ...regardless of how basic or how 'tough'.
We run and have for over 20 years an audio and video production business. My wife and I are both experienced, high performance rated pilots and live in Alaska. It's paramount we fly with the business as we're living in an area nearly the physical size of the entire lower 48 with over 3 million lakes (sorry Minnesota, but we do only have just over 10,000 rivers;))---& more coastline that the ENTIRE CONUSA. With a pair of roads. No access without a plane or boat, or big balls and a four wheeler or snow 'machine' (it's Alaskan for snowmobile;)). We've been lucky enough to work with plenty of the largest cable and network broadcasters on documentaries and 'real TV' (not reality). Whether following the Troopers, fishing for crabbing on the ocean, flying into single resident 'zip codes' in the dead of winter with 2400 pounds of heating fuel in the plane with ya, it can be a kick in the ass and iOS has changed our operations in the last half decade for the better. Filing my FP, deciding how much fuel, traffic and weather conditions as well as updated Jep charts, plates and diversions ...it's becime my kneeboard, fifty LB flight bag, manuals and checklists, as well as maintenance and troubleshoot instructions ...ADSB and TCAS, 3D terrain mapping and tradfic following, it's a BIG change. While the Note 3 works GREAT for sketching rigging points with structural engineers, etc. The rMBP has been an absolute Home Run for us as has the new Mac Pro at the studios. We use several HP and Dell workstations as well, both systems are awesome and I think I'm one of the few enjoying Win 8.1 ...bought an HP 2in1 for about $750 and I've got a 13" core i5 slate with an SSD.
Way TL/DR; youngsters don't be afraid to open your eyes and think for yourself. Try everything. Use what your need and stay away from the internet when you've made your chouce for a couple of weeks:). Something better is ALWAYS around the corner but each and every choice available today is better than yesterday's. Guaranteed
timbo24 - Tuesday, September 30, 2014 - link
Great review, thanks for the hard work.gevorg - Tuesday, September 30, 2014 - link
Very nice to see audio tests, just another thing that makes Anandtech reviews unique.paul4na - Wednesday, October 1, 2014 - link
Unique? If you want proper phone reviews with detailed benchmarks then go to GSMArena.doobydoo - Wednesday, October 1, 2014 - link
LOL. You made a funny.slatanek - Tuesday, September 30, 2014 - link
still no sign of Windows 10 event...Chaser - Tuesday, September 30, 2014 - link
As objectively as I could I took up Costco on their 14 day return policy and tried the iPhone 6. I owned the first iPhone and had been Android flagship type ever since.Bottom line: compared to Android the iPhone does less. After 5+ years the interface is STILL the same square blobs that float on the screen. No shortcuts. No app widgets. Install a new app and it is placed in the next open spot with all the other square blobs. I liek how I can use shortcuts for my higher use app but hide others in the application folder with Android.
No notification LED. My new G3 I can color code that notification to know just by sight what type of alert has popped up on my phone. Text, email, Facebook, more. With Apple you get a flash of the camera, if its upside down. What a joke.
Despite Apple "allowing" Swiftkey's new keypad its a paltry joke compared to Android's version. Chrome can also be installed but make no mistake, any links through email or text will open the default browser Safari. iMessage is still the default text client with no alternatives that provide the same functionality.
It's simple. While the Apple faithful will buy their new tech darling phones the boring, long on the tooth Apple interface does less. Android offers far more customization and openness. Back my gold iPhone 6 went to Costco and now I love my new G3. Sigh...maybe another 5 years.
Parhel - Tuesday, September 30, 2014 - link
The customization and openness is exactly what turns me off of Android. It's not the only thing, but it's the main thing. I don't want that in a phone. I spend 10 hours a day coding and troubleshooting at work. For a phone, I want something that's already set up for me. Something that I barely need to even look at to use. I don't want to tinker with it.Chaser - Tuesday, September 30, 2014 - link
I tinker with nothing if I chose. However I'd rather have those choices than Apple's divine vision of how my phone should operate.