ECC outside critical path?

By: anonymou5 (no.delete@this.spam.com), September 16, 2022 3:50 pm
Room: Moderated Discussions
hobold (hobold.delete@this.vectorizer.org) on September 16, 2022 1:03 pm wrote:
> groo (charlie.delete@this.semiaccurate.com) on September 16, 2022 11:06 am wrote:
>
> > It takes time to compute ECC data and L1s tend to be a bit tight on timings.
>
> ECC computations might not have to be in the critical path. For example a load operation
> could forward its data without ECC check; sometime later you'd do the ECC computations;
> at the retire stage you would verify that the data and ECC codes match. On mismatch you'd
> have to replay from the erroneous load forward, possibly with a corrected error.
>
> Obviously, bit errors would have to be really rare for this to make sense. If the goal is to
> get higher yield with more redundancy in the L1 cache, then ECC errors are expected to be a
> somewhat common occurrence, and this suggested scheme probably costs too much performance.

Ah yes, more "let me speculate ahead" stuff. Which has gone so damn well for us all.

Hear that faint giggle? That is Spectre, sitting in its dark corner, waiting for you.

"But this is different." I hear you say. "Since it's not under the attacker's control."

"Uhm... you just haven thought it through enough. Please stay away from CPU design."

...

Please take the above with good humor. I'm simply trying to point out how hard this is.
If it were easy, we'd be done with it by now. But, alas, we're not. Spectre is hard to
eliminate. And even though we have managed to stomp out a few instances of it, others
have crept into the designs since 2017/2018. Precisely because designers still are not
thinking things through. More humility and more 🍊 needed. :)
< 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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