N2, or V1?

By: Rayla (rayla.delete@this.example.com), December 4, 2021 2:20 pm
Room: Moderated Discussions
Adrian (a.delete@this.acm.org) on December 4, 2021 2:33 am wrote:
> Wilco (wilco.dijkstra.delete@this.ntlworld.com) on December 3, 2021 1:58 pm wrote:
> > Adrian (a.delete@this.acm.org) on December 3, 2021 10:51 am wrote:
> > > G (108106020.delete@this.nitt.edu) on December 3, 2021 9:25 am wrote:
> > > > Adrian (a.delete@this.acm.org) on December 3, 2021 8:52 am wrote:
> > > > > Adrian (a.delete@this.acm.org) on December 3, 2021 8:47 am wrote:
> > > > > > Anon (no.delete@this.thanks.com) on December 3, 2021 6:52 am wrote:
> > > > > > > Kara (karaardalan.delete@this.gmail.com) on December 3, 2021 6:36 am wrote:
> > > > > > > > none (none.delete@this.none.com) on December 3, 2021 6:19 am wrote:
> > > > > > > > > Kara (karaardalan.delete@this.gmail.com) on December 3, 2021 6:05 am wrote:
> > > > > > > > > > Adrian (a.delete@this.acm.org) on December 3, 2021 5:51 am wrote:
> > > > > > > > > > >
> > > > > > > > > > > https://www.nextplatform.com/2021/12/02/aws-goes-wide-and-deep-with-graviton3-server-chip/
> > > > > > > > > > >
> > > > > > > > > > >
> > > > > > > > > >
> > > > > > > > > > The N2 is described much wider here than Arm has ever disclosed.
> > > > > > > > > > I hate it when companies do this, like give some info what's gonna happen?
> > > > > > > > >
> > > > > > > > > What description of N2 is there in that article? I only see guesses.
> > > > > > > >
> > > > > > > > I meant the guesses, it's so not ARM to design 8 wide decode and 15 wide issue
> > > > > > > > mArchs. 64kb l1i cache wouldn't be able to keep up Nor the punly ROBs, how
> > > > > > > > do you feed such a wide core? Without smt or legendry l1i and rob?
> > > > > > > >
> > > > > > > > Neoverses are targeted toward server processors, making them wider doesn't make any sense.
> > > > > > >
> > > > > > > I thought that this was the V1 core? Aimed at maximum perf per thread.
> > > > > >
> > > > > >
> > > > > > Amazon did not disclose which core they have used, but what was said matches better N2 than V1.
> > > > > >
> > > > > > Choosing N2 also makes more sense for Amazon, because they are more interested in
> > > > > > general-purpose performance within a given power consumption than on performance
> > > > > > when only few threads are active or performance for floating-point applications.
> > > > > >
> > > > > >
> > > > > >
> > > > > >
> > > > > >
> > > > > >
> > > > > >
> > > > >
> > > > >
> > > > > Moreover, Graviton 3 uses 100 W for 64 cores.
> > > > >
> > > > > After subtracting uncore power, the power limit per core will be 1.25 W at most.
> > > > >
> > > > > This power level is below what a core from the X1/X2/V1 series requires, which is in the 2 ... 3 W range.
> > > > >
> > > > >
> > > > > Power levels in the range 1 ... 1.5 W per core are the target for N1/N2.
> > > > >
> > > > > This is an additional reason to believe that Graviton 3 uses N2.
> > > > >
> > > > >
> > > > >
> > > > >
> > > > >
> > > > >
> > > >
> > > > I think Graviton3 uarch matches exactly with cortex-V1.
> > > >
> > > > https://i2.wp.com/semianalysis.com/wp-content/uploads/2021/12/7.jpg?w=2048&ssl=1
> > > > https://images.anandtech.com/doci/16640/Neoverse_V1_13_575px.png
> > >
> > >
> > > Some parts of the slides do indeed match well.
> > >
> > > We do not know which are the customization options provided by ARM for V1.
> > >
> > > From these slides, it looks like the core used in Graviton 3 is indeed based on V1, but with
> > > some parts deleted to lower the power consumption, e.g. with only half of the SVE datapath.
> >
> > That doesn't make any sense. As the optimization guide clearly states, V1 can either run
> > 4 128-bit Neon FMAs or 2 256-bit SVE FMAs. Both use the same 4 128-bit pipes. Obviously.
> >
> > > In that case the Graviton 3 cores, being slightly cut and used at a relatively low clock
> > > frequency, to be able to work within the 100 W TDP, should have intermediate performance
> > > and energy efficiency characteristics between an N2 and a V1 in maximum configuration.
> >
> > +60% on all-core SPECFP_rate doesn't exactly look like a minor gain, neither does this. The +60%
> > means at just 2.6GHz it beats EPYC 7763 at 3.5GHz on fprate while using a fraction of the power.
> >
> > Wilco
> >
>
> Yes, but the Graviton 3 slides show 1 x 256 SVE, not 2 x 256 SVE.
>
> This was also mentioned on the NextPlatform site, by someone who presumably has seen the
> complete presentation, as the reason why he did not believe that the core is a V1.
>
> However most of the other parts of the slides match V1, including the ARMv8.5-A compliance.
>
>
>
>

What slide shows that it only has one 256b SVE pipe? All they say is that they have 256b SVE - which is in line with what the V1 has. It's not different from Intel saying that ICL and SKL-SP have 512b AVX, despite having multiple 512b datapaths.
< Previous Post in ThreadNext Post in Thread >
TopicPosted ByDate
Some info about the Amazon Graviton 3Adrian2021/12/03 06:51 AM
  Some info about the Amazon Graviton 3Kara2021/12/03 07:01 AM
    Some info about the Amazon Graviton 3---2021/12/03 10:03 AM
      Some info about the Amazon Graviton 3Kara2021/12/03 10:45 AM
  Some info about the Amazon Graviton 3Kara2021/12/03 07:05 AM
    Some info about the Amazon Graviton 3none2021/12/03 07:19 AM
      Some info about the Amazon Graviton 3Kara2021/12/03 07:36 AM
        N2, or V1? Anon2021/12/03 07:52 AM
          N2, or V1? Adrian2021/12/03 09:47 AM
            N2, or V1? Adrian2021/12/03 09:52 AM
              N2, or V1? G2021/12/03 10:25 AM
                N2, or V1? Adrian2021/12/03 11:51 AM
                  N2, or V1? Wilco2021/12/03 02:58 PM
                    N2, or V1? Adrian2021/12/04 03:33 AM
                      N2, or V1? -.-2021/12/04 04:37 AM
                      N2, or V1? Rayla2021/12/04 02:20 PM
                        N2, or V1? Adrian2021/12/05 01:15 AM
                          N2, or V1? dmcq2021/12/05 02:43 AM
                            N2, or V1? Adrian2021/12/05 03:54 AM
                              N2, or V1? ---2021/12/05 11:45 AM
                                N2, or V1? Adrian2021/12/05 01:07 PM
                                  Other (minor) power factors?Paul A. Clayton2021/12/06 07:37 AM
                    N2, or V1? Anon2021/12/04 10:53 PM
                      N2, or V1? Andrei F2021/12/05 04:22 AM
                Only 4 ALUsJörn Engel2021/12/03 07:37 PM
                  Only 4 ALUsWilco2021/12/04 09:54 AM
          N2, or V1? -.-2022/05/24 06:34 AM
            Graviton3 on Chip &CheesePer Hesselgren2022/06/17 06:19 AM
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