Data integrity of L1 caches

By: --- (---.delete@this.redheron.com), September 16, 2022 5:25 pm
Room: Moderated Discussions
anon2 (anon.delete@this.anon.com) on September 16, 2022 5:49 pm wrote:
> --- (---.delete@this.redheron.com) on September 16, 2022 11:28 am wrote:
> > anon2 (anon.delete@this.anon.com) on September 15, 2022 7:04 pm wrote:
> > > Everybody knows the data integrity problems with parity protected write-back arrays. ECC has also
> > > seemed to be a difficult problem for L1 data cache that seems like nobody has solved very well.
> > >
> >
> > > What is expensive about L1 ECC which is less costly in
> > > L2? Keep in mind you need write-through, so L2 has to
> > > receive all the stores.
> >
> > ECC saves bits (relative to simpler options like replication) by performing math across
> > the ENTIRE line. This means that each time you modify an element of L1, something (whether
> > in the core itself or in the L1) will have to read the entire line (whether before or
> > after the write) to calculate the new ECC value. That's a lot of extra power.
> >
> > L2 is different because the entire line is written at once
> > from the L1 to the L2, so there's a one-time calculation.
>
> Uh, obviously that's not the case in a write-through L1 design.

Who still uses write-through L1's? (In "normal" computing, not weird cases like micro-controllers or whatever.)
< Previous Post in ThreadNext Post in Thread >
TopicPosted ByDate
Data integrity of L1 cachesanon22022/09/15 06:04 PM
  Data integrity of L1 cachesGroo2022/09/15 10:46 PM
    Data integrity of L1 cachesanon22022/09/16 08:00 AM
      Data integrity of L1 cachesgroo2022/09/16 10:06 AM
        ECC outside critical path?hobold2022/09/16 12:03 PM
          ECC outside critical path?Mr. Camel2022/09/16 02:39 PM
            ECC outside critical path?anonymou52022/09/16 04:01 PM
          ECC outside critical path?anonymou52022/09/16 03:50 PM
            ECC outside critical path?hobold2022/09/17 05:57 AM
        Data integrity of L1 cachesanon22022/09/16 04:45 PM
  Data integrity of L1 cachesanon.12022/09/16 05:51 AM
    Data integrity of L1 cachesanon22022/09/16 08:04 AM
      Data integrity of L1 cachesBrett2022/09/16 11:12 AM
  Data integrity of L1 caches---2022/09/16 10:28 AM
    Data integrity of L1 cachesdmcq2022/09/16 12:41 PM
      Data integrity of L1 caches---2022/09/16 01:42 PM
    Data integrity of L1 cachesanon22022/09/16 04:49 PM
      Data integrity of L1 caches---2022/09/16 05:25 PM
        Read the thread (NT)anon22022/09/16 05:55 PM
        Data integrity of L1 cachesanon22022/09/16 05:57 PM
    Data integrity of L1 cachesMichael S2022/09/17 04:02 PM
  Data integrity of L1 cachesDavid Kanter2022/09/16 08:44 PM
    ECC word not necessarily full cache linePaul A. Clayton2022/09/17 09:59 AM
      ECC word not necessarily full cache lineDavid Kanter2022/09/18 11:29 AM
        ECC word not necessarily full cache lineAnon2022/09/18 11:54 AM
          ECC word not necessarily full cache linehobold2022/09/18 05:32 PM
            ECC word not necessarily full cache lineMichael S2022/09/19 07:47 AM
              ECC word not necessarily full cache linehobold2022/09/20 05:38 AM
                ECC word not necessarily full cache linedmcq2022/09/21 04:10 AM
                ECC word not necessarily full cache lineMichael S2022/09/21 05:55 AM
                  ECC word not necessarily full cache linehobold2022/09/21 12:59 PM
  Data integrity of L1 cachesDavid Hess2022/09/17 09:03 AM
  Data integrity of L1 cachesMichael S2022/09/17 04:12 PM
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