Cortex-A72 Technical Reference Manual

By: Wilco (Wilco.Dijkstra.delete@this.ntlworld.com), March 7, 2015 8:50 am
Room: Moderated Discussions
David Kanter (dkanter.delete@this.realworldtech.com) on March 7, 2015 12:43 am wrote:
> Wilco (Wilco.Dijkstra.delete@this.ntlworld.com) on March 6, 2015 2:31 pm wrote:
> > Brett (ggtgp.delete@this.yahoo.com) on March 6, 2015 12:57 pm wrote:
> > > David Kanter (dkanter.delete@this.realworldtech.com) on March 6, 2015 12:42 am wrote:
> > > > > 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. ;)
> > >
> > > 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.
> >
> > Yeah ARM is to blame, after all Intel only added AES early 2010...
>
> I'm not blaming anyone. I'm saying it's ridiculous to make inferences about general performance using benchmarks
> that are skewed by the presence of AES instructions (that goes for any designs, not just ARM).

Given we all understand exactly how much skew there is, it means you can actually make very good inferences. It is also possible to remove the AES result if necessary. It doesn't change the fact that A57 shows far more than 20% IPC gain on Geekbench.

> > > > 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.
> > >
> > > Unless IBM gets into the ARM64 business Intel is going to dominate the GCC comparison
> > > for the next two decades, longer than I expect Intel to survive as dominate company.
> > > $15 SOC's don't generate the sort of revenues that justify optimizing for GCC.
> >
> > GCC is a hard benchmark indeed but it's not going to cost billions of dollars to design next
> > generation CPUs that do better. Did Athlon64 cost billions? All it took was a brilliant design
> > and a great team to make it happen. The trend is obvious, each new generation of ARM cores improves
> > by 30-50%. I wonder what would happen if say the Athlon64 designer does an ARM...
>
> The IPC for ARM cores is improving much more slowly than that. It's also hard to discuss the overall
> performance since ARM doesn't control the power management, process, memory controller, etc.

Just consider A8->A9->A15->A57. Geekbench single-threaded result increases 10x from 600MHz A8 to 2.1GHz A57. That's a 42% IPC gain per generation plus a 52% clock frequency gain. Are you denying that?

Wilco
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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
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              Cortex-A72 Technical Reference ManualDavid Kanter2015/03/06 11:43 PM
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                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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