none (none.delete@this.none.com) on November 27, 2013 2:08 am wrote:
> anon (anon.delete@this.anon.com) on November 26, 2013 6:42 pm wrote:
> > none (none.delete@this.none.com) on November 26, 2013 10:18 am wrote:
> > > Michael S (already5chosen.delete@this.yahoo.com) on November 26, 2013 9:06 am wrote:
> > > > none (none.delete@this.none.com) on November 26, 2013 7:20 am wrote:
> > > > > anon (anon.delete@this.anon.com) on November 26, 2013 6:53 am wrote:
> > > > > > Eric (eric.kjellen.delete@this.gmail.com) on November 26, 2013 4:05 am wrote:
> > > > > > > Linus Torvalds (torvalds.delete@this.linux-foundation.org) on November 25, 2013 12:29 pm wrote:
> > > > > > > > And the old Atom really was pretty bad at some general-purpose stuff. That VR-zone link
> > > > > > > > says KNL is 72 modified Silvermont cores, so it should be much better in that regard.
> > > > > > > >
> > > > > > > > Linus
> > > > > > >
> > > > > > > What I am mostly interested in is exactly how they are modified
> > > > > > > with regard to vector processing. The Knights
> > > > > > > Corner cores and those of its predecessors were basically P54C derivatives with an added 512-bit vector
> > > > > > > unit (for 16 DP FMA flops per core and cycle) but as we
> > > > > > > speculated in a different branch of the thread (what
> > > > > > > is now "3-TFLOPS-DGEMM") 72 Silvermont cores with a single 512-bit vector unit will not be enough to give
> > > > > > > the cited 3 DP peak TFLOPS at a reasonable clock frequency (they would have to run at 2.6 GHz).
> > > > > >
> > > > > > Why is 2.6GHz an unreasonable frequency?
> > > > > >
> > > > > > Intel's 14nm silvermont derivative is reported to have 2.7GHz clock.
> > > > >
> > > > > Try to put 72 of them along with 2 wide vector units and you'll see that doesn't seem
> > > > > reasonable even on 14nm :-)
> > > >
> > > > Yes, judged by Avaton C2750, when running at max. frequency 72
> > > > Silvermont cores alone, without VPUs, would eat over 150W.
> >
> > How do you calculate that? Compare between C2550 and C2750, and you add 6W TDP for 4
> > cores (plus 2MB L3, inteconnect, etc, but ignore that). Then reduce power by 30% for
> > 14nm. That comes out at 1.05W per core at 2.4GHz (presumably). Increase frequency to
> > 2.6 probably brings power up significantly, but it seems 72 cores could fit into 100W.
>
> You think the VPU won't come with increased power?

No.

> Do you know that on Haswell as soon
> as the AVX unit gets used voltage is increased (at least that's what happen on my
> system)? Have you ever seen Haswell power consumption skyrocket as soon as AVX is
> heavily used? And that's with a 256-bit SIMD unit.
>
> Then you have to add eDRAM, interconnect, etc.
>
> > > > But why did you mention "2 wide vector units"? At 2.7 GHz one unit per core will do the job.
> > >
> > > You're right. But current rumors point to Silvermont + dual VPU, so in that context
> > > saying 14nm next gen Atom can reach 2.7 GHz kind of assumes these rumors are correct,
> > > so 2 VPUs :-)
> >
> > No it doesn't! The whole point is to derive how they can achieve
> > 3 TFLOPS. If it runs at 2.6GHz, then it requires 1 vector unit.
>
> OK, if you insist, but IMHO that still won't fit.

Ok, then what are your estimates?