Enough with the idiocy ... let's have proper ECC again.

By: David Kanter (dkanter.delete@this.realworldtech.com), December 17, 2020 12:04 pm
Room: Moderated Discussions
Maynard Handley (name99.delete@this.name99.org) on December 17, 2020 9:42 am wrote:
> Etienne Lorrain (etienne_lorrain.delete@this.yahoo.fr) on December 17, 2020 9:26 am wrote:
> > Maynard Handley (name99.delete@this.name99.org) on December 17, 2020 9:09 am wrote:
> > > Björn Ragnar Björnsson (bjorn.ragnar.delete@this.gmail.com) on December 16, 2020 10:09 pm wrote:
> > > > Adrian (a.delete@this.acm.org) on December 16, 2020 7:31 am wrote:
> > > > > Gabriele Svelto (gabriele.svelto.delete@this.gmail.com) on December 15, 2020 3:24 pm wrote:
> > > > > > It seems like Intel has added support for what they call in-band ECC to their recent Atom SoCs, see the
> > > > > > mention here as well as here. There isn't much in the way of details on Intel pages apart from the
> > > > > > fact that the mechanism can correct single-bit errors in
> > > > > > non-ECC memory (presumably by reducing its effective
> > > > > > size). However a Google search turned out this patent. All-in-all a very welcome development.
> > > > >
> > > > >
> > > > > The support for In-Band ECC also exists in Tiger Lake U, but it is disabled in almost all SKUs,
> > > > > including in most of the "Embedded" SKUs, where I would have expected it to be enabled.
> > > > >
> > > > > It is enabled only in the Tiger Lake U "Embedded" SKUs for the Extended Temperature Range.
> > > > >
> > > > > In-Band ECC allows the use of ECC with the LPDDR4x memories, but this advantage is paid
> > > > > by a slight reduction in memory capacity and by a reduction in speed that is difficult to
> > > > > quantify, because in most cases the extra accesses for ECC can be cached (the worst but
> > > > > very seldom case is to do twice as many memory accesses, both for data and for ECC).
> > > > >
> > > > >
> > > > > Intel has a patent application for it
> > > >
> > > > The padawans here may not know that back in the day, even after they were born, it was
> > > > as simple as pie to order simms and dimms with parity/ecc at little additional cost.
> > > >
> > > > Sure, if you didn't care about ECC you could shave off a few percentage points on
> > > > the price of memory. Big deal, but not for everybody, I'd always go for the slightly
> > > > more expensive option (at least I could use it in system that supported it).
> > > >
> > > > Then something happened which changed the DRAM landscape forever (hopefully not forever though).
> > > > What happened? Intel started producing processors that had no, absolutely no, nada, ability to implement
> > > > ECC. These CPUs have for the last two decades been by far the bulk of processors sold. Could you
> > > > have undetected memory errors? Yes, it's a near certainty. Could these have had serious consequences?
> > > > Hard to say, are you working on anything that could have serious consequences?
> > > >
> > > > At a guess, an ECC capable DIMM costs 5-9% more to get to an end user than one that is
> > > > without ECC. I'm willing to pay more than that for such a "fancy" feature, but oh-no, it's
> > > > nearly impossible to source un-buffered ECC ram at reasonable speeds and/or prices.
> > > >
> > > > This in-line ECC appears to be a colossal kludge, presented as
> > > > a feature, to solve a problem that never should have existed.
> > > >
> > > > > https://www.freepatentsonline.com/y2019/0332469.html
> > > > >
> > > > > which should have been rejected, because it describes good methods to implement
> > > > > In-Band ECC, but which are completely obvious and are exactly like anyone would
> > > > > implement it if given the task, without any other prior knowledge.
> > > >
> > > >
> > >
> > > From the startup log on an M1 boot...
> > > 10.281418 AppleFireStormErrorHandler AppleARM64ErrorHandler: will not panic on correctible ECC errors
> > >
> >
> > That is nice not to panic on correctible ECC error (instead
> > of panic-ing, just correct the error and log the address).
> > Obviously a correctible ECC error on a protected memory area (i.e. even the OS
> > cannot read) would need to panic if the correction is not done in hardware.
> > Now the question is also, do you only correct the read value (risking un-correctible error
> > if another bit error appears on that address), or do you write-back the correction?
> > Next step is not to panic on uncorrectible ECC error, just reload if possible,
> > or kill only the task affected (or only the virtual machine affected).
>
> It all remains unclear.
> One possibility is that this refers PURELY to ECC in caches (so not especially interesting).
>
> Another is that there's the possibility for in-line ECC but this is not yet hooked up?
>
> Another is that there is genuine in-line ECC, working exactly as you would
> hope (and presumably with RAS functionality being added over time, eg even
> a non-correctable error in a block of memory that also exists on disk).
>
> That's all even apart from the issue of how the OS intervenes. Hopefully
> over the next year or so people will figure out more details.

LPDDR doesn't have ECC, so I am skeptical that Apple uses ECC memory.

I think your interpretation that it's ECC on caches is more likely to be correct.

I don't think Apple has the volume to develop non-standard LPDDR memory interfaces and modules. But I could be wrong, and it would be awesome if they did.

David
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TopicPosted ByDate
In-band ECC support in recent Atom SoCsGabriele Svelto2020/12/15 03:24 PM
  In-band ECC support in recent Atom SoCsanon2020/12/15 05:40 PM
  In-band ECC support in recent Atom SoCsanon32020/12/15 07:07 PM
  In-band ECC support in recent Atom SoCsEtienne Lorrain2020/12/16 01:48 AM
    In-band ECC support in recent Atom SoCsAdrian2020/12/16 07:43 AM
      ECC in SoCsKonrad Schwarz2020/12/17 07:37 AM
        ECC in SoCsAdrian2020/12/17 08:43 AM
          ECC in SoCsMichael S2020/12/17 12:06 PM
  In-band ECC support in recent Atom SoCs & Tiger Lake UAdrian2020/12/16 07:31 AM
    In-band ECC support in recent Atom SoCs & Tiger Lake UJS2020/12/16 09:07 PM
      In-band ECC support in recent Atom SoCs & Tiger Lake UGabriele Svelto2020/12/16 10:00 PM
        In-band ECC support in recent Atom SoCs & Tiger Lake UJS2020/12/17 12:39 AM
          In-band ECC support in recent Atom SoCs & Tiger Lake UEtienne Lorrain2020/12/17 02:15 AM
            In-band ECC support in recent Atom SoCs & Tiger Lake UJames2020/12/17 07:28 AM
              In-band ECC support in recent Atom SoCs & Tiger Lake UEtienne Lorrain2020/12/17 09:16 AM
                In-band ECC support in recent Atom SoCs & Tiger Lake Urwessel2020/12/17 09:51 AM
                  In-band ECC support in recent Atom SoCs & Tiger Lake UMichael S2020/12/17 12:22 PM
    Enough with the idiocy ... let's have proper ECC again.Björn Ragnar Björnsson2020/12/16 10:09 PM
      Enough with the idiocy ... let's have proper ECC again.Maxwell2020/12/17 12:58 AM
        Enough with the idiocy ... let's have proper ECC again.pixiespeed2020/12/17 09:04 AM
      Enough with the idiocy ... let's have proper ECC again.Adrian2020/12/17 07:40 AM
      Enough with the idiocy ... let's have proper ECC again.Maynard Handley2020/12/17 09:09 AM
        Enough with the idiocy ... let's have proper ECC again.Etienne Lorrain2020/12/17 09:26 AM
          Enough with the idiocy ... let's have proper ECC again.Maynard Handley2020/12/17 09:42 AM
            Enough with the idiocy ... let's have proper ECC again.David Kanter2020/12/17 12:04 PM
              Enough with the idiocy ... let's have proper ECC again.Doug S2020/12/17 01:03 PM
              Enough with the idiocy ... let's have proper ECC again.phonon2020/12/17 03:25 PM
                Internal array ECC vs. memory controllerDavid Kanter2020/12/19 10:39 AM
                  Internal array ECC vs. memory controllerJörn Engel2020/12/20 10:42 AM
                    Internal array ECC vs. memory controllerrwessel2020/12/20 10:52 AM
                    Internal array ECC vs. memory controllerDavid Kanter2020/12/20 03:44 PM
              Enough with the idiocy ... let's have proper ECC again.Maynard Handley2020/12/17 04:55 PM
                Enough with the idiocy ... let's have proper ECC again.rwessel2020/12/17 07:34 PM
                  Enough with the idiocy ... let's have proper ECC again.Maynard Handley2020/12/17 09:10 PM
                    Enough with the idiocy ... let's have proper ECC again.Maynard Handley2020/12/17 09:43 PM
                      Enough with the idiocy ... let's have proper ECC again.Maynard Handley2020/12/18 09:30 AM
                        Enough with the idiocy ... let's have proper ECC again.anon22020/12/19 01:00 AM
                          Enough with the idiocy ... let's have proper ECC again.Maynard Handley2020/12/19 10:23 AM
                            Enough with the idiocy ... let's have proper ECC again.anon22020/12/19 03:01 PM
                              Enough with the idiocy ... let's have proper ECC again.Maynard Handley2020/12/19 04:23 PM
                                Enough with the idiocy ... let's have proper ECC again.anon22020/12/19 04:30 PM
              Enough with the idiocy ... let's have proper ECC again.Björn Ragnar Björnsson2020/12/17 07:41 PM
                Enough with the idiocy ... let's have proper ECC again.David Hess2020/12/19 08:48 PM
              Enough with the idiocy ... let's have proper ECC again.Memory Guy2020/12/17 09:19 PM
      Enough with the idiocy ... let's have proper ECC again.rwessel2020/12/17 10:01 AM
      Enough with the idiocy ... let's have proper ECC again.Wes Felter2020/12/18 09:38 PM
        Thanks for the confirmation!David Kanter2020/12/19 11:51 AM
          Thanks for the confirmation!Konrad Schwarz2020/12/20 09:34 AM
            Thanks for the confirmation!Niels Jørgen Kruse2020/12/20 11:01 AM
              Thanks for the confirmation!David Kanter2020/12/20 03:45 PM
              Thanks for the confirmation!Gionatan Danti2020/12/21 12:50 AM
                Thanks for the confirmation!Niels Jørgen Kruse2020/12/21 09:07 AM
            Thanks for the confirmation!David Kanter2020/12/20 03:42 PM
              Thanks for the confirmation!Foo_2020/12/21 02:01 AM
                Thanks for the confirmation!David Kanter2020/12/21 08:39 AM
            Thanks for the confirmation!Paul2020/12/20 11:29 PM
              Thanks for the confirmation!Michael S2020/12/21 01:00 AM
                Thanks for the confirmation!anon20202020/12/21 01:44 AM
                Thanks for the confirmation!Paul2020/12/22 12:42 PM
                  Thanks for the confirmation!Michael S2020/12/22 02:28 PM
                    Thanks for the confirmation!Paul2020/12/22 06:12 PM
                      Thanks for the confirmation!Michael S2020/12/23 02:55 PM
                        Thanks for the confirmation!Paul2020/12/23 03:54 PM
                          Thanks for the confirmation!Dan Fay2020/12/23 04:38 PM
                            Thanks for the confirmation!Paul2020/12/26 04:10 AM
                              Thanks for the confirmation!Björn Ragnar Björnsson2020/12/26 08:37 PM
                                Thanks for the confirmation!anon22020/12/27 02:00 AM
                                Thanks for the confirmation!Doug S2020/12/28 12:47 PM
            Thanks for the confirmation!David Hess2020/12/21 06:35 PM
              Thanks for the confirmation!Konrad Schwarz2020/12/22 12:08 AM
                Thanks for the confirmation!Doug S2020/12/22 10:42 AM
                  Thanks for the confirmation!David Hess2020/12/22 12:32 PM
                Thanks for the confirmation!David Hess2020/12/22 12:21 PM
        Enough with the idiocy ... let's have proper ECC again.Björn Ragnar Björnsson2020/12/19 04:25 PM
          Enough with the idiocy ... let's have proper ECC again.Brett2020/12/19 08:13 PM
            Enough with the idiocy ... let's have proper ECC again.David Hess2020/12/19 09:17 PM
              Enough with the idiocy ... let's have proper ECC again.Konrad Schwarz2020/12/21 03:29 AM
                Enough with the idiocy ... let's have proper ECC again.David Hess2020/12/21 06:49 PM
            Enough with the idiocy ... let's have proper ECC again.Björn Ragnar Björnsson2020/12/19 09:57 PM
              Enough with the idiocy ... let's have proper ECC again.Björn Ragnar Björnsson2020/12/19 10:14 PM
            Enough with the idiocy ... let's have proper ECC again.Adrian2020/12/20 02:06 AM
              Enough with the idiocy ... let's have proper ECC again.rwessel2020/12/20 08:43 AM
             Multi-level DRAM?Brett2020/12/20 08:07 PM
               Multi-level DRAM?Heikki Kultala2020/12/21 11:58 AM
               Multi-level DRAM?David Hess2020/12/21 07:25 PM
                 Multi-level DRAM?Adrian2020/12/22 05:15 AM
                   Multi-level DRAM?Dan Fay2020/12/22 10:11 AM
                     Multi-level DRAM?Paul2020/12/22 06:01 PM
                       Multi-level DRAM?Dan Fay2020/12/23 12:29 PM
                         Multi-level DRAM?Paul2020/12/23 01:00 PM
                           Multi-level DRAM?Dan Fay2020/12/23 04:30 PM
                             Multi-level DRAM?David Hess2020/12/23 05:05 PM
                           Multi-level DRAM?Björn Ragnar Björnsson2020/12/25 06:44 PM
                             Multi-level DRAM?Paul2020/12/26 04:04 AM
                               Multi-level DRAM?Michael S2020/12/26 08:11 AM
                                 DIMM binsPaul2020/12/26 08:55 AM
                                   DIMM binsBjörn Ragnar Björnsson2020/12/26 08:09 PM
                                     DIMM binsBjörn Ragnar Björnsson2020/12/26 08:19 PM
                                       DIMM binsDaniel Fay2020/12/27 07:51 PM
                                  Is binning at the module or die level? (NT)anonymous22020/12/27 02:36 PM
                                    Is binning at the module or die level?David Hess2020/12/28 01:31 PM
                               Multi-level DRAM?Doug S2020/12/28 12:55 PM
                               Multi-level DRAM?David Hess2020/12/28 01:36 PM
                             Multi-level DRAM?anon­­32020/12/26 10:22 PM
                               Multi-level DRAM?Björn Ragnar Björnsson2020/12/27 07:12 PM
                               Multi-level DRAM?Paul2021/01/04 04:20 AM
               Multi-level DRAM?Carson2021/01/05 12:14 PM
                 Multi-level DRAM?Brett2021/01/05 02:05 PM
        Enough with the idiocy ... let's have proper ECC again.Björn Ragnar Björnsson2020/12/19 04:35 PM
        Enough with the idiocy ... let's have proper ECC again.David Hess2020/12/19 08:59 PM
          Enough with the idiocy ... let's have proper ECC again.rwessel2020/12/20 08:56 AM
          Enough with the idiocy ... let's have proper ECC again.Doug S2020/12/20 10:16 AM
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