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.

Introduction A8’s CPU: What Comes After Cyclone?
Comments Locked


View All Comments

  • annah_souls - Tuesday, October 28, 2014 - link

    Yes, it's my money and I have a lot of them to buy as much as iPhone as I like. If you don't satisfy Apple product, you may not but $2000 handbag also. Pity you to yell Apple "The world is not fair!" LOL
  • Donkey2008 - Wednesday, October 29, 2014 - link

    People with intelligence don't buy purely on specs, which it seems 100% of Android owners do. I can just picture you like the many Android fanboys I have met....."Deeeerp, it has foure cores witch iz twice as mony as en iPhone so itz twice as fast, Deeeerrp".

    Enjoy your clunky, resource-hog, half-baked Google OS, your extremely inefficient hot-and-crispy quad-core space heater SOC (which has to be throttled by Android so the phone doesn't melt LULZ) and premium plastic-wrapped junk.
  • leonhk1 - Wednesday, October 29, 2014 - link

    I have stock of Brand New Apple iPhone 6 - 64GB Unlocked phones for sale at $650 only, sealed in box with 1 year warranty. Available in Gold , silver and space grey colors

    Interested buyer should E-mail me at: megas83@yahoo.co.uk
  • iphone 3 - Friday, October 31, 2014 - link

    I am wondering if you guys have similar analysis for ipad air 2 A8x
  • odedia - Tuesday, November 4, 2014 - link

    Please check the NAND differences between the 64gb model and the 128gb model. It appears the 128gb model uses TLC and not MLC.
  • curiosity - Thursday, November 6, 2014 - link

    output power / voltage: per channel or combined?
  • sellcheapli - Monday, November 24, 2014 - link

    Apple iPhone 6 - Plus 4G 16GB , 64GB , 128GB (Grey,Silver,Gold) ... $600
  • sellcheapli - Monday, November 24, 2014 - link

    Apple iPhone 6 - Plus 4G 16GB , 64GB , 128GB (Grey,Silver,Gold) ... $600

    Apple iPhone 6 - 16GB , 64GB , 128GB (Grey,Silver,Gold) ... $500

    Message : sellcheaplimited@gmail.com
  • Apple_iPhone_Service - Thursday, April 30, 2015 - link


    Find the best Iphone Service center in your area in Chennai & Bangalore

    iphone service center in Anna Nagar | iphone service center in Mogappair | iphone service center in Thirumangalam | iphone service center in Perambur | iphone service center in Egmore | iphone service center in Kilpauk | iphone service center in Aminjikarai | iphone service center in Koyambedu | iphone service center in Kodambakkam | iphone service center in Nungambakkam | iphone service center in TNagar | iphone service center in Royepettah | iphone service center in Mylapore | iphone service center in Teynampet | iphone service center in Saidapet | iphone service center in Guindy | iphone service center in Ashok Nagar | iphone service center in KK Nagar | iphone service center in Saligramam | iphone service center in Virugambakkam | iphone service center in Chrompet | iphone service center in Pallavaram | iphone service center in Tambaram | iphone service center in Velachery | iphone service center in Thiruvanmiyur | iphone service center in Adyar | iphone service center in OMR | iphone service center in ECR | iphone service center in Medavakkam | iphone service center in Madipakkam | iphone service center in Perumbakkam | iphone service center in Pallikaranai | iphone service center in Sholinganallur | iphone service center in Gopalapuram | iphone service center in Besant Nagar | iphone service center in Washermenpet | iphone service center in Broadway | iphone service center in Purusawalkam
    iphone service center in koramangala | iphone service center in jayanagar | iphone service center in jp nagar|iphone service center in btm | iphone service center in ulsoor | iphone service center in kammanahali | iphone service center in cox town \ iphone service center in frazer town | iphone service center in mathikere | iPhone Service Center in kempapura | iphone service center in marathalli | iphone service center in hsr | iphone service center in electronic city | iphone service center in sg playa | iphone service center in Bellandur | iphone service center in Domlur | iphone service center in Malleswaram | iphone service center in Rajajinagar | iphone service center in majestic | iphone service center in forum mall | iphone service center in Sony world signal | iphone service center in echo space | iphone service center in forum mall | iphone service center in Whitefield

    We provide wide-range of Hardware & Software services for all branded smartphones and tablets including brands like APPLE, SAMSUNG, HTC, SONY, LG, MOTOROLA, MICROMAX, LENOVO etc. can recover the smartphone devices from any sort of problems like physical damage, Water lock and replacing the core components like Display , IC's, Front and Rear Camera components and other hardware/software issues.
    Topics Discus under Training Program:
    Soldering, De-soldering of components, Check of voltages in a battery of a mobile phone, Use of SMD reworks station, Triggering of batteries, Assembling & disassembling of mobile phones, Chip level servicing of components: Power amplifiers (pf), audio IC (Cobba), CPU (Mad), Power supply IC (Cont), Charging Control IC (Chaps). Rf Signal Processor IC (Hagar). Also well versed with SMD components replacement (Capacitors, Diodes Resistors, and LED’s). Rebelling & repair of ball grade array ICs (BGA).
    Hardware Complaint Service Training:
    Mobile Complaints: Dead, network, display problem, keypad problem, display light problem, keypad light problem, touchpad problem, sensor problem, head phone jack problem, speaker problem, mic problem, ringer problem, charging problem, Bluetooth problem, wifi problem, camera problem, volume button problem, camera button problem, on off switch problem, strip problem, fm problem, network problem, dead, water lock, hanging problem, handset off problem, restart issue
    Software Complaint Service Training:
    Phone unlock, pattern lock, vibrator problem, navigation key problem, Contact service, hanging, partial dead, network, unlocking, Flashing various software like USR, twister, tornado, griffin, UFS, Uni Box for color, camera, blue tooth, infrared enabled mobile phones of Nokia, Samsung, Panasonic, Ericson, Sony, Siemens, LG, Motorola and many more
    Motherboard Complaint Service Training:
    Ic (integrated circuit), Smd ic (leg type), bga ic (ball type)capacitor, Resister ,transistor, filter, fuse, diode, power crystal, clock crystal connector, battery connector ,usb jack, charging jack, head phone chack, inner key pad, vibrator ,speaker, mic, ringer

    Koramangala 5th block
    no 75/8,kristal prestige 4th floor, idea show room upstairs,opp to bhima jewellers,
    koramangala industrial layout, 5th block, 7026604420/ 7026604423

    Koramangala 7th block
    no 340, maruthi plaza,1st b cross,koramangala 7th block
    opp to forum road,behind A2B, 08041521112

    Koramangala 1st Block
    no 16,vijith plaza,80ft road,koramangala 1st block
    opp to reliance fresh, 08041521115

    jayanagar 4th block
    Diamond Arcade,no 21,east 11th main,32nd d cross,jayanagar 4th block
    opp to kalamandir & mom and me,near cool joint signal

    jayanagar 9th block
    no 1339,41st cross,25th main,jayanagar 9th block
    opp to central mall road,behind jain college,next to himalaya store

    Banashankari 1st stage
    no 5,Sln complex,80 ft road,srinivasa nagar circle,banashankari 1st stage
    near bata showroom

    Banashankari 2nd stage
    no31, 21st main road, near bda complex,banashankari 2nd stage
    near goli vada pav
    08049570768 / 9980090798

    Rajajinagar 6th block
    no 246,Dr.Rajkumar Road,Rajajinagar 6th block
    next to nea albek hotel & sangeetha mobile showroom

    no 10,2nd main,sampige main road.near mantri mall,
    opp to albek hotel,below to samsung show room
    malleswaram, 08041474313

    28/3, Sai Shekar complex,H.M.T Main Road, Beside Subbaiah Hospital
    08041573366 / 9611269682

    Door no-3, 21st main road, sri Rajeshwari New Colony, Hebbal,
    Kempapura Main Road, Bangalore
    08042103355 / 9611269682

    no 49&50, guru gowtham complex,SV road,next to metro station,
    below to manak jewellers , ulsoor, 08041520642

    no 11,service road,old airport road,next to hyundai showroom,befor sony show room
    domlur in towards mg road, 08041103602

    Frazer town
    no 64/1, concord plaza, coles road, frazer town, near shanthi sagar hotel

    no 17,mathu mansion,kammanahalli circle near,opp to ganesha temple
    below to liberty showroom, 08041103592

    no 746,Tayapa towers,13th main,7th cross,near udupi garden,opp to dominas,icici,peter england
    below to mumbai kitchen , 08041500208

    no 2580, 27th main, 13th cross,next to PHD

    No 71/1a,opp to swarnamukhi hospital,univercell upster,sarjapura main road
    next to bellandur total mall, 08042060460

    Jp Nagar 7th Phase
    no 243, Brigate Apartment signal opposite, jp nagar 7th phase

    No: 35/1B, CRM SOWBHAGYA ANNEXE, Shop No.2,Varthur Main Road,
    marathahalli bridge next,Munnekolala,

    VV puram

    Anna nagar
    no 18, TNSCB shopping complex,near jsp honda showroom,
    thirumangalam junction water tank,anna nagar west,

    no 25,sambantham garden,100ft road tharamani link road,opp to karaikudi hotel near TCS
    velachery, 04442139797

    no 64/4, sri vidhya avenue,omr ptc main road,opp to kfc restaurant

    Anna nagar-2
    Muva’s arcade,C52/4,anna nagar east,near chinthamani roundana circle, opp to girias


    No 2 ,North usman Road,Kodambakkam Road Junction ,Near Motherhood T-nagar,
    below Mallika mansion Chennai-17

    apple iphone service center in abu dhabi
    apple iphone service center in abu dhabi
    iphone service center in abu dhabi
    apple iphone service center in dubai
    apple iphone authorized service center in dubai
    apple iphone authorised service centre in dubai
    apple iphone service center in dubai
    apple iphone authorized service center in dubai
    apple iphone authorised service centre in dubai
    apple iphone authorized service center in dubai
    apple iphone authorised service centre in dubai
    iphone service center in bur dubai
    iphone service center in deira dubai
    iphone service dubai
    iphone service dubai
    iphone service center dubai
    iphone service in dubai
    apple iphone service center uae
    apple iphone service centre uae
    apple iphone service center uae
    apple iphone service centre uae
    apple iphone service center dubai
    apple iphone service center in uae
    apple iphone service centre in uae
  • raj parihar - Tuesday, November 3, 2015 - link

    mcf doesn't have any Multiply operations. In A8, its benefiting from a better (tuned) prefetcher possibly with negative (-3 or -1) stride.

Log in

Don't have an account? Sign up now