Infinity Fabric = PCIe

By: Ricardo B (ricardo.b.delete@this.xxxxx.xx), March 16, 2017 11:30 pm
Room: Moderated Discussions
Michael S (already5chosen.delete@this.yahoo.com) on March 16, 2017 5:13 pm wrote:
> Ricardo B (ricardo.b.delete@this.xxxxx.xx) on March 16, 2017 3:07 pm wrote:
> > Michael S (already5chosen.delete@this.yahoo.com) on March 16, 2017 2:46 pm wrote:
> > > Aaron Spink (aaronspink.delete@this.notearthlink.net) on March 16, 2017 11:11 am wrote:
> > > > Michael S (already5chosen.delete@this.yahoo.com) on March 16, 2017 9:54 am wrote:
> > > >
> > > > > No, full QPI link consists from 4 quadrants, each with his own clock.
> > > > >
> > > > Pretty sure it is a single fwd clk per link which agrees with
> > > > "Each link also has one and only one forwarded clock."
> > > >
> > > > While it is true that QPI has flexibility in quadrant allocation, the clk isn't replicated
> > > > according to the public documentation. The individual lanes undergo an in depth training
> > > > procedure and support periodic retraining. Can't remember if there is a disparity mechanism
> > > > or not but it seams reasonable that at higher speeds it would be required.
> > >
> > > Yes, see above.
> > > BTW, what is "disparity mechanism" ?
> >
> > Some mechanism to ensure it doesn't send too many consecutive 1 or 0.
>
> Thanks. I never encountered it by name "disparity mechanism".
> I probably invented a dozen of various schemes for such purpose in different shipping
> products, all without knowing that I construct disparity mechanisms. :-)
>
> > Even for DC coupled links, it can help with the behaviour of transmitter/receiver.
> > A popular one is, of course, 8B/10B (or 64B/66B) encoding.
>
> 8B/10B both assures high density of transitions and guarantees near-perfect DC balance.
> In DC-coupled linked the later is unnecessary.

A colleague was designing a 1 Gbit/s LVDS transmitter.
Even on simulation, it misbehaved with very long sequences of "1" or "0".
On the other hand, for a DC balanced signal like a clock or 8B/10B coded data, it worked fine.
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TopicPosted ByDate
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      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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