back to article ARM Cortex-A73: How a top-end mobe CPU was designed from scratch

For its latest top-end smartphone processor core – the Cortex-A73 – ARM designed its microarchitecture more or less from scratch. Whereas its predecessor, 2015's Cortex-A72, was drawn up in Austin, Texas, the new A73 microarchitecture was designed by a team in France, starting about three years ago. Although we're told the …

  1. Lotaresco Silver badge

    El Reg employs puppet as journalist?

    " In a loop, for example, the CPU will quickly realize a jump to the start of the loop is taken, and only the final check when the loop is over will its prediction miss."

    Yoda making comment are you. Five pounds claim do I.

    1. diodesign (Written by Reg staff) Silver badge

      Re: El Reg employs puppet as journalist?

      I deserve that. I think I was trying to be poetic.


      1. Tom 7 Silver badge

        Re: El Reg employs puppet as journalist?

        Reverse Poetic Newsgarble.

      2. Simon Harris Silver badge

        Re: El Reg employs puppet as journalist?

        Don't believe you - if you were being poetic it would be more like...

        In a repeating loop, e.g.,

        The CPU will quickly see

        a jump to the start is often taken,

        and only the final time will it be mistaken.

      3. DropBear

        Re: El Reg employs puppet as journalist?

        "I deserve that."

        Absolutely no need to apologize - you should be proud to have a brain with integrated out-of-order execution...!

  2. Michael H.F. Wilkinson Silver badge

    We do live in interesting times (in a good way)

    if a CPU this powerful needs less than a square mm.

    Hats off (mine is the Tilley, today) to all scientists and engineers who have allowed us to come from Colossus all the way to this tiny CPU

  3. This post has been deleted by its author

    1. Anonymous Coward
      Anonymous Coward

      Re: Vulnerabilities

      Shouldn't make a difference, pipelines stall all the time. The CPU it still executing the right instruction sequence, the probability thing is guessing which instructions to pre-execute to speed things up. If it guesses wrong its wasted a bit of heat.

    2. Steve Todd Silver badge

      Re: Vulnerabilities

      How about never? Branch prediction isn't something code sees. If the prediction is correct then code executes seamlessly. If it misses then there's a pipeline stall while the correct instructions are loaded and executed. Your code has no sight over or access to the predictor, and it is still subject to the memory management unit allowing it access the code in the first place.

      1. Anonymous Coward
        Anonymous Coward

        Re: Vulnerabilities

        I think I mostly agree with you, except Rowhammer shows that previously unseen levels of complexity can allow for previously unseen creative approaches to exploits.

        Still, what could possibly go wro

  4. Mage Silver badge

    Core alone less than 0.65mm2 in size

    Can we have a chip with GPU, 128G RAM and 32G Flash, dedicated SDIO for SDcard, and 2 x USB2go, as well anything else useful for interfacing to wired and wifi and a bunch of other stuff for any random application other than a phone?

    Two versions:

    1) BGA

    2) Cut down I/O in 80 pin SMT leaded package (no external memory or parallel bus interfaces) for easy DIY designs. You can solder those by reflow using a regular soldering iron. Can be same chip with simply a different package.

    JTAG obviously, but a simple standardised "BIOS" option to overwrite even a "bricked" Flash via USB or SDIO/Micro SD would be nice.

    Five pins to five onboard DAC optionally routed to GPU would allow any driver selected option of:

    1) 3 high speed DAC (Software defined RF) and 2 x DAC up to 192kHz sample rate

    2) Composite, RGB SCART, Y/C, Component or VGA (PAL, NTSC, HD up to 1600 x 1200)

    1. Anonymous Coward
      Anonymous Coward

      Re: Core alone less than 0.65mm2 in size

      128GB of on-chip memory is a tough ask... but I think you mean 128MB.

      It seems to me that processors, DRAM, and flash are very distinct segments of the semiconductor market. Maybe because DRAM and flash are highly commoditised and without the volumes that they are sold in, the DDR/flash in a SoC would turn out much more expensive than separate ICs alongside the SoC.

      But I suspect that there is a more fundamental reason these 3 strands of technology have not been seen in integrated form.

      For your hobbyist requirements, the best solution is a module - and there are some that get close - e.g. Trenz TE0722 which is a 40-pin DIP module with an ARM+FPGA chip (with ADC), boot flash, microSD, but no off-chip RAM.

      I reckon flash is not a problem as a second chip, but DRAM requires a lot of interface pins which is probably why it isn't on this module.

  5. Chz

    "From scratch"

    Not really. It's a logical evolution of the A9/A17 design, which was always better suited to phones than the A57/A72 was. It's only because Apple did the "but we have 64 bits!" thing that this architecture was sidelined until now. They most certainly did not start with a blank canvas - anyone familiar with A17 will see the lineage.

    That's not to knock their achievements, of course. It looks fantastic, and because we've been on the A72 line for the past couple of releases it's got quite a lot more going on than its A17 grandfather does due to the amount of time they've had to invest in it.

    I know the article mentions this, but the headline and the PR department claims still rankle a bit.

    1. Mage Silver badge

      Re: "From scratch"

      File -> New and then copy paste blocks from Library


      File -> Existing Documents, Save As, then edit.

      1. Anonymous Coward
        Anonymous Coward

        Re: "From scratch"

        @ Mage.

        But that's not "From scratch".

        The definition of from scratch is : "from the beginning, without using anything that already exists:", and variations of that.

        Taking any existing data, templates or documents, is therefore by definition, not from scratch.

        1. Anonymous Coward
          Anonymous Coward

          Re: "From scratch"

          So is mixing dough from pre-made flour in a pre-crafted bowl. If you really want to get anal, you can only make bread from scratch by starting with a crop of wheat seeds, growing the grain from the beginning, raising chickens and cows from birth in order to harvest their goods, and so on.

          IOW, this term isn't one you can really take literally or nothing would get done.

          1. Anonymous Coward
            Anonymous Coward

            Re: "From scratch"

            chickens and cows? keep it simple, N E ful knows that to make bread you just need wheat and a crafting table (and maybe some bone meal to grow the wheat quickly, so slay some skeletons while you're waiting).

    2. diodesign (Written by Reg staff) Silver badge

      Re: "From scratch"

      " know the article mentions this, but the headline and the PR department claims still rankle a bit."

      Yeah, yeah, all right. I did point out it's based on the A17 and the opening line says "more or less from scratch" – I couldn't really squeeze it into the headline. The A73's microarchitecture borrows a lot of the A17's structure, but various crucial parts have been rewritten like the branch prediction and memory system... if you take a broom and change the stick, head and bristles, I don't think you've got the same broom.


      1. Boothy Silver badge

        Re: "From scratch"

        Triggers the expert on brooms, best go talk to him. :-)

  6. TiddlyPom

    How about an octal-core ARM based laptop/netbook?

    Looking at the power efficiency of ARM vs x86, why oh why don't we have any decent ARM based Netbooks? As a Linux user myself, I would like to see an Ubuntu ARM based laptop - Canonical sit up and take note please! Recently I set up a Raspberry Pi 3 (with an mSATA SSD) to run Ubuntu Mate 16.04. I expected it to be very laggy and barely usable but in fact it is a very usable little machine and can run Firefox, Thunderbird, LibreOffice or almost anything I want to on it (I have even run the Eclipse IDE on it)! The 1GB RAM is a bit restrictive although having swap on the mSATA SSD helps. Now imagine (say) a laptop with a 2GHz octal core 64 bit ARM CPU and a decent amount of memory (lets say 8GB) running full desktop Ubuntu Unity with (say) a 256GB mSATA SSD and then imagine the battery life and usability. Chromebooks (with Android Apps) are good but full a Linux laptop would be better. Come on guys, your ARM chips can do far more than just run phones!

    1. roselan

      Re: How about an octal-core ARM based laptop/netbook?

      My wild uneducated guess: It's more profitable to plant a cpu in a phone (or a tablet) than in a laptop.

      Windows doesn't play well with arm, that leaves chromebooks. And chromebooks are fine with crouton and linux. So what's your issue with linuxed chromebooks? They are decent hardware i believe.

      1. TiddlyPom

        Re: How about an octal-core ARM based laptop/netbook?

        Absolutely no problem with Chromebooks and yes they are great hardware. My workhorse Linux laptop is a second hand Chromebook (Acer C710 from eBay @ £92) with CoreBoot reflashed with SeaBIOS running Ubuntu 16.04 LTS (updated to 8GB RAM and with a 128GB SSD). Great little laptop - love it - but this is not an installation process that the majority of people would be able (or willing) to do. Yes I know you can do the Crouton thing but if you accidentally 'reset' your Chromebook you wipe out your data. If somebody would sell a laptop set up (from boot) to run Ubuntu, Linux Mint (or another similar easy-to-use distribution) even if it was x86 (like the Acer C710) that would be great (especially using CoreBoot). What would be BETTER would be an ARM laptop which is just as powerful but uses 1/2 or 1/4 of the power.

    2. werdsmith Silver badge

      Re: How about an octal-core ARM based laptop/netbook?

      Looking at the power efficiency of ARM vs x86, why oh why don't we have any decent ARM based Netbooks?

      I would be interested in ditching Intel too, but I suspect that a more efficient CPU isn't going to make a huge difference in a Netbook, Notebook, Laptop etc, until someone fixes display technology so a backlight is only required in the dark EBook style. Currently LCD based displays try to deal with bright conditions by out-brighting them thus sucking power to the backlight and they always lose when they fight the sun.

      It's different for phones because they keep their backlight off and we put it on to view stuff briefly. On a productive computer display, it remains permanently on for hours.

      I do have an Intel Celery based Chromebook with a HDMI screen, runs Ubuntu with KDE nicely too, for about 6.5 hours.

    3. Bruce Hoult

      Re: How about an octal-core ARM based laptop/netbook?

      The Pi3 is quite nice. I have one on my desk. But I also have an Odroid XU4, possibly the best bang for the buck in ARM boards.

      The XU4 is $74 vs $35 for the Pi. But it's not actually twice the price, because you have to add at minimum an SD card to both, which is going to cost you a bit for a decent sized fast one. You also have to add a power supply to the Pi, which is probably going to set you back $20+. The XU4 comes with a 20 W power supply.

      If you want a headless server to SSH into then you're done. Otherwise, add keyboard, mouse, monitor to both and the price difference starts to look trivial.

      Once that's sorted out, the XU4 also has:

      - about 2.5x the CPU power in each the main 4 cores (not even counting the LITTLE ones)

      - 2 GB of fast DDR3 RAM vs 1 GB

      - gig ethernet vs 100

      - four or five times faster SD card interface (when used with a good card)

      - PLUS an eMMC interface that is twice as fast as the SD card

      - USB3 vs USB2

      What's missing on the XU4?

      - WIFI, Bluetooth, and 3.5mm sound out (but HDMI has sound)

      The XU4 competes closely per core with a similar MHz core/core2. Think "White MacBook" of 2008 MacBook Air or something like that. But it's got twice as many (fast) cores.

      1. Old Used Programmer

        Re: How about an octal-core ARM based laptop/netbook?

        I don't know where you're getting your PSUs for Pi3B boards, but I can get good ones from a reputable supplier for $6.

    4. P0l0nium

      Re: How about an octal-core ARM based laptop/netbook?

      FYI ... There is no "power efficiency of ARM vs x86"

      In servers X86 wins hands down on "efficiency" .. even on an equivalent process.

      And its been possible to make a power competitive X86 smartphone for the past 2 generations

      Intel's problem is not "power efficiency" ... Its the management, the culture and the inability to cut corners without screwing up !!

      1. FoxyRaider

        Re: How about an octal-core ARM based laptop/netbook?

        There is no power efficiency advantage in theory in either direction. The CPU ISA on either chip, if having same adequate resources, process node etc would come out roughly similar in speed and efficiency.

        Intel 'wins hands down' as you say purely because they have been building Server Chips for a lot longer than ARM and have a more mature architecture in this respect

        ARM are catching up fast with the recently announced next generations AppliedMicro X-Gene 3 and Cavium ThunderX2 arriving in same performance envelope as the middle range Intel xenon designs

        What is just as important is the various ecosystems that support and create 'moats' against competition.

        Intel arguably discovered this when trying to compete with ARM in the Smartphone. They also failed over a number of years to pull off an integrated modem solution which is vital for SOC mobile acceptance.

        ARM in reverse has to compete with the Intel/Microsoft 'moat' and Server Software which has allowed Intel a near monopoly status in CPU Server market. If there was a genuine competition Intel wouldn’t be able to charge their eye watering (Server) prices. AMD is certainly a problem here at failing to offer genuine performance on their current line up of CPUs. Perhaps Zen will be different,

  7. earl grey Silver badge


    I recall the term "mobe" being banned from el Reg years ago. Did someone lift the skirts on that?

    1. LaeMing

      Re: MOBE

      I prefer the descriptive contraction 'MoFo'

  8. anonymous boring coward Silver badge

    "A 10nm A73 core is a little less than 0.65mm2 in size, making it ARM's smallest ARMv8-a core, allowing the architecture to keep up with the demand for thinner and thinner phones. Smaller chip equals thinner phone, hopefully."

    Yeah... It's mm^2, not inch^2. And it's not mounted standing on its edge in its package.

  9. P0l0nium

    Process or Architecture ???

    They got 30% more performance using a 10nm process that offers errrrrr..... 40% more performance.

    Am I missing something here or does this Emperor have no clothes ??

    1. anonymous boring coward Silver badge

      Re: Process or Architecture ???

      Obviously they decided to not use that last extra 10%...

POST COMMENT House rules

Not a member of The Register? Create a new account here.

  • Enter your comment

  • Add an icon

Anonymous cowards cannot choose their icon

Biting the hand that feeds IT © 1998–2020