Cortex-A72 Technical Reference Manual

By: Jouni Osmala (josmala.delete@this.cc.hut.fi), March 7, 2015 1:54 am
Room: Moderated Discussions
> > > > A57 is definitely more than 20% faster at the same clock, as you can easily conclude
> > > > from various benchmarks (eg. Geekbench shows 40% single threaded gain overall
> > > > in AArch32 mode between Galaxy S5 and Galaxy S6 at the same clock).
> > >
> > > That's a bogus comparison since Geekbench contains lots of AES
> > > stuff, and ARM64 contains special instructions for AES.
> >
> > Are you accusing ARM of pulling an Intel, making sure that benchmarks are dominated
> > by feature X right before Intel adds feature X to the instruction set. ;)
>
> No, I'm saying that anyone making claims about A57 vs. A15 is being disingenious
> if they do not acknowledge the impact of highly workload specific instructions.
>
> It's one thing for Oracle to include database accelerators, when
> they own the database and it's a fairly important workload.
>
> It's a totally different thing for Intel, AMD, ARM, or whoever, to claim that AES acceleration
> via dedicated hardware will impact general workloads in a meaningful way.
>
> > This tactic is old hat, blatantly obvious for over a decade. Happy
> > to see that ARM is playing by the rules of the CPU market.
>
> > > What's the speedup on GCC?
> >
> > GCC is the worst pointer chasing spaghetti on the planet. You have to brute force tweak hundreds
> > of CPU details so as not to get burned by one of a hundred glass jaws that will cripple your
> > performance. This takes billions of dollars that AMD does not have, much less tiny ARM.
>
> That's the real world. Most code is terrible and optimizing
> it is hard. That's how CPU designers create value.
>
> Anyone can optimize a loop that regularly accesses arrays. Dealing with
> branches, irregulat data structures, etc. is the interesting stuff.
>
> David

No actually CPU designers create value by creating faster CPU:s for target workload. There are seminars telling C++ programmers that what you call interesting case is generally slow and you should try to make it more like the less interesting case because that's faster on all architectures than the interesting stuff. Its more like Game programmers teaching others how to design applications that have higher performance on given hardware. In real world there are four kinds of code from CPU design point, crappy but fast enough, crappy but too slow, and code that is designed to run nicely that is either fast enough or too slow. And for ARM sacrificing power efficiency of other classes for crappy but too slow is totally out of question like for Intel the making opposite choice is also out of question because of different workloads.
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Cortex-A72 Technical Reference ManualRonald Maas2015/03/05 07:01 AM
  Cortex-A72 Technical Reference Manualdmcq2015/03/05 10:01 AM
  Cortex-A72 Technical Reference ManualAlberto2015/03/05 10:06 AM
    Cortex-A72 Technical Reference ManualExophase2015/03/05 11:57 AM
      Cortex-A72 Technical Reference ManualAlberto2015/03/06 09:45 AM
        Cortex-A72 Technical Reference ManualWilco2015/03/06 11:49 AM
          Cortex-A72 Technical Reference ManualAlberto2015/03/06 01:09 PM
            Cortex-A72 Technical Reference ManualWilco2015/03/07 08:37 AM
          Cortex-A72 Technical Reference Manualjuanrga2015/03/06 05:18 PM
    Cortex-A72 Technical Reference ManualHugo Décharnes2015/03/05 02:40 PM
      Cortex-A72 Technical Reference ManualWilco2015/03/05 03:28 PM
        Cortex-A72 Technical Reference ManualHugo Décharnes2015/03/05 11:32 PM
        Cortex-A72 Technical Reference ManualDavid Kanter2015/03/05 11:42 PM
          Cortex-A72 Technical Reference ManualHugo Décharnes2015/03/06 01:55 AM
            Cortex-A72 Technical Reference Manualnone2015/03/06 02:36 AM
              Cortex-A72 Technical Reference ManualHugo Décharnes2015/03/06 03:08 AM
                Cortex-A72 Technical Reference Manualnone2015/03/06 03:12 AM
                Cortex-A72 Technical Reference ManualWilco2015/03/06 03:39 AM
          Cortex-A72 Technical Reference ManualWilco2015/03/06 04:04 AM
            Cortex-A72 Technical Reference Manualnone2015/03/06 04:50 AM
              Cortex-A72 Technical Reference ManualWilco2015/03/07 08:26 AM
                Cortex-A72 Technical Reference Manualnone2015/03/09 12:10 AM
                  Cortex-A72 Technical Reference Manualdmcq2015/03/09 01:14 AM
                    Cortex-A72 Technical Reference Manualnone2015/03/09 01:53 AM
          Cortex-A72 Technical Reference ManualBrett2015/03/06 11:57 AM
            Cortex-A72 Technical Reference ManualKlimax2015/03/06 12:39 PM
            Cortex-A72 Technical Reference ManualExophase2015/03/06 01:22 PM
            Cortex-A72 Technical Reference ManualWilco2015/03/06 01:31 PM
              Cortex-A72 Technical Reference Manualjuanrga2015/03/06 05:22 PM
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              Cortex-A72 Technical Reference ManualDavid Kanter2015/03/06 11:43 PM
                Cortex-A72 Technical Reference Manualjuanrga2015/03/07 05:16 AM
                Cortex-A72 Technical Reference ManualWilco2015/03/07 08:50 AM
                  Cortex-A72 Technical Reference ManualDavid Kanter2015/03/08 01:30 AM
                    Cortex-A72 Technical Reference ManualMichael S2015/03/08 03:14 AM
                    Cortex-A72 Technical Reference ManualHugo Décharnes2015/03/08 03:26 AM
                      Cortex-A72 Technical Reference Manualjuanrga2015/03/08 05:51 AM
                        Cortex-A72 Technical Reference ManualHugo Décharnes2015/03/08 06:08 AM
                    Cortex-A72 Technical Reference ManualKlimax2015/03/08 07:44 AM
                  Cortex-A72 Technical Reference ManualGabriele Svelto2015/03/08 03:01 AM
              Cortex-A72 Technical Reference Manualanon2015/03/07 10:41 AM
            Cortex-A72 Technical Reference ManualDavid Kanter2015/03/06 11:37 PM
              Cortex-A72 Technical Reference ManualExophase2015/03/06 11:45 PM
              Cortex-A72 Technical Reference ManualJouni Osmala2015/03/07 01:54 AM
              Cortex-A72 Technical Reference Manualhashhash2015/03/07 06:06 AM
      Cortex-A72 Technical Reference Manualnone2015/03/05 11:36 PM
        Cortex-A72 Technical Reference ManualHugo Décharnes2015/03/06 01:47 AM
          Cortex-A72 Technical Reference Manualnone2015/03/06 02:29 AM
            Cortex-A72 Technical Reference ManualHugo Décharnes2015/03/06 03:02 AM
        Cortex-A72 Technical Reference Manualjuanrga2015/03/06 08:38 AM
          Cortex-A72 Technical Reference ManualJouni Osmala2015/03/06 09:27 AM
      Cortex-A72 Technical Reference ManualAlberto2015/03/06 09:58 AM
        Cortex-A72 Technical Reference ManualExophase2015/03/06 10:52 AM
          Cortex-A72 Technical Reference ManualAlberto2015/03/06 02:30 PM
            Cortex-A72 Technical Reference Manualjuanrga2015/03/06 05:32 PM
            Cortex-A72 Technical Reference ManualRonald Maas2015/03/06 07:11 PM
              Cortex-A72 Technical Reference ManualAlberto2015/03/07 05:52 AM
                Cortex-A72 Technical Reference ManualRonald Maas2015/03/07 08:52 AM
  Cortex-A72 Technical Reference ManualNoSpammer2015/03/05 11:33 AM
  Add two more differences.Jouni Osmala2015/03/05 02:13 PM
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