Infinity Fabric = PCIe

By: Ricardo B (ricardo.b.delete@this.xxxxx.xx), March 16, 2017 5:30 am
Room: Moderated Discussions
Aaron Spink (aaronspink.delete@this.notearthlink.net) on March 16, 2017 1:08 am wrote:
> Ricardo B (ricardo.b.delete@this.xxxxx.xx) on March 15, 2017 11:02 pm wrote:
> > slacker (s.delete@this.lack.er) on March 15, 2017 10:45 pm wrote:
> > > Michael S (already5chosen.delete@this.yahoo.com) on March 15, 2017 4:19 pm wrote:
> > > > slacker (s.delete@this.lack.er) on March 15, 2017 2:59 pm wrote:
> > > > >
> > > > > The emperor has no clothes; I suspect AMD is literally using PCIe as an interprocessor interconnect, with a
> > > > > cHT protocol layered on top.
> > > >
> > > > Why do you suppose so?
> > > > It seems to me, it is technically possible to use the same electrical drivers/receivers
> > > > for both PCIe or HT3. In FPGAs they are doing it routinely for as long as they
> > > > started to support differential I/O at PCIe Gen2 or higher speed.
> > >
> > > I considered that, but is AMD willing to implement two controllers (PCIe + HT) on each
> > > Naples chip, and then share the transceivers (and maybe the serdes blocks)? The PCIe
> > > controllers and switches for half the PCIe lanes (64x) will be sitting unused.
> >
> > Even if they tried to build on top of PCIe, they need an additional
> > block to implement their CC protocol on top of PCIe.
> > And PCIe (or any form of multi-lane serial link) isn't the best option for _latency_.
> >
> > Side note: HT is a parallel point to point bus. Not much
> > to share with PCIe, besides pins and I/O cells, I think.
>
> Would still be multi-lane serial. Best case is that you could reuse the raw SERDES/Phit layer and plug the link/packet/protocol
> layers above it. Kind of hard to do multiple different phi layers on top of the same I/Os. In all existing
> case where multiple protocol engines can share I/Os, they either use the same signalling technology or are extremely


Yes, at the physical layer they need to be similar enough to share the same I/O cells.
Which means some sort of differential current mode signaling, which is the case.

But beyond that, there's considerable freedom, as long as you can afford the die space.
Eg, after the input cells, you can feed the signals to otherwise distinct:
a) Infitiny Fabric (IF) input blocks
b) PCIe input blocks

No need for IF to be multi-lane serial, which in my definition of multi-lane serial implies a pretty long RX/TX pipeline (serializer/deserializer, 64B/66B encoder/decoder, FIFO, lane matching logic).

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TopicPosted ByDate
What is infinity fabric?slacker03/12/17 06:41 PM
  What is infinity fabric?Jason Creighton03/13/17 12:26 AM
    What is infinity fabric?Klimax03/13/17 12:42 AM
      What is infinity fabric?Kevin G03/13/17 04:39 AM
  What is infinity?Anon03/13/17 04:44 AM
  What is infinity fabric?Groo03/13/17 07:33 AM
    What is infinity fabric?Ireland03/13/17 09:12 AM
      Another way to put same questionIreland03/13/17 09:16 AM
      What is infinity fabric?Groo03/13/17 12:12 PM
        What is infinity fabric?Ireland03/13/17 02:07 PM
          What is infinity fabric?Ireland03/13/17 02:32 PM
            What is infinity fabric?Seni03/14/17 12:38 PM
          What is infinity fabric?Brendan03/14/17 05:28 AM
            What is infinity fabric?Ireland03/14/17 06:09 AM
            What is infinity fabric?Groo03/14/17 07:35 AM
              What is infinity fabric?Ireland03/14/17 08:35 AM
    Infinity Fabric = PCIeslacker03/15/17 02:59 PM
      Infinity Fabric = PCIeMichael S03/15/17 04:19 PM
        Infinity Fabric = PCIeIreland03/15/17 04:49 PM
        Infinity Fabric = PCIeRicardo B03/15/17 10:25 PM
        Infinity Fabric = PCIeslacker03/15/17 10:45 PM
          Infinity Fabric = PCIeRicardo B03/15/17 11:02 PM
            Infinity Fabric = PCIeAaron Spink03/16/17 01:08 AM
              Infinity Fabric = PCIeRicardo B03/16/17 05:30 AM
                Infinity Fabric = PCIeAaron Spink03/16/17 10:58 AM
        Infinity Fabric = PCIeGabriele Svelto03/16/17 03:48 AM
          Latency vs. bandwidthDavid Kanter03/16/17 08:04 AM
      Infinity Fabric = PCIeGroo03/15/17 05:35 PM
        Infinity Fabric = PCIeslacker03/15/17 11:11 PM
          Infinity Fabric = PCIeAdrian03/16/17 02:51 AM
            Infinity Fabric = PCIeMichael S03/16/17 04:32 AM
              Infinity Fabric = PCIeAdrian03/16/17 07:58 AM
                Infinity Fabric = PCIeRicardo B03/16/17 09:16 AM
                  Infinity Fabric = PCIeMichael S03/16/17 09:54 AM
                    Infinity Fabric = PCIeRicardo B03/16/17 10:07 AM
                      Infinity Fabric = PCIeMichael S03/16/17 02:33 PM
                        Infinity Fabric = PCIeGabriele Svelto03/17/17 03:35 AM
                          Infinity Fabric = PCIeAaron Spink03/17/17 10:25 AM
                            Thanks, your posts on this thread have been extremely informative (NT)Gabriele Svelto03/17/17 01:08 PM
                            Infinity Fabric = PCIeRicardo B03/17/17 06:08 PM
                              Infinity Fabric = PCIeAaron Spink03/17/17 06:27 PM
                              Quickpath papers - circuits and implementationslacker03/18/17 06:50 PM
                                Quickpath papers - circuits and implementationRicardo B03/19/17 08:07 AM
                    Infinity Fabric = PCIeAaron Spink03/16/17 11:11 AM
                      Infinity Fabric = PCIeMichael S03/16/17 02:46 PM
                        Infinity Fabric = PCIeRicardo B03/16/17 03:07 PM
                          Infinity Fabric = PCIeMichael S03/16/17 05:13 PM
                            Infinity Fabric = PCIeAaron Spink03/16/17 11:04 PM
                            Infinity Fabric = PCIeRicardo B03/16/17 11:30 PM
                              Infinity Fabric = PCIeMichael S03/17/17 07:24 AM
                                Infinity Fabric = PCIeRicardo B03/17/17 06:07 PM
              Infinity Fabric = PCIeDavid Kanter03/16/17 08:36 AM
                Infinity Fabric = PCIeMichael S03/16/17 08:50 AM
                  Infinity Fabric = PCIeAaron Spink03/16/17 11:24 AM
                    Infinity Fabric = PCIeMichael S03/16/17 02:45 PM
                      Infinity Fabric = PCIeAaron Spink03/16/17 11:21 PM
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