Core 2 Errata -- problematic or overblown?

By: Linus Torvalds (torvalds.delete@this.osdl.org), June 27, 2007 5:10 pm
Room: Moderated Discussions
Matt Sayler (sayler@thewalrus.org) on 6/27/07 wrote:
>
>How significant were the TLB handling changes?

I'd say: "Totally insignificant".

The biggest problem is that Intel should just have
documented the TLB behavior better. The Core 2 changes
are kind of gray area, and the old documentation simply
didn't talk about the higher-level page table structures
and the caching rules for them.

So that part is just a good clarification, and while it
could be called a "bug" just because older CPU's didn't
do that caching, I don't think it's an errata per se.

Of course, if you depended on it not happening (and a
lot of people did), it's painful. But it really does make
the architecture definition better and clearer.

(I don't think Linux needed any software changes at all for
the TLB semantics clarification, although that was largely
just due to luck - we had mis-used the TLB earlier, and
fixing that software bug we rewrote the page table handling
to be more robust, which means that the spec update from
Intel didn't affect us at all, afaik).

>In general, do Core2 chips seem to be more or less buggy
>than previous iterations? Are errata par for the course
>as we approach billion-transistor commodity MPUs?

Pretty much all CPU's have always had errata, and the
commodity CPU's usually have much fewer of them than the
boutique ones.

So this has nothing to do with billion-transistor MPU's,
or about commodity. CPU's always have bugs. And embedded
(or vendor-specific) CPU's tend to actually have more of
them, since they are often easier to work around by just
saying "don't do that, then".

So Intel and AMD actually tend to fix the bugs a lot more
aggressively than you'd see for some single-vendor thing,
simply because they don't control the stack the way other
architectures generally do.

I'd expect other CPU's to generally have more errata
than most commodity x86 chips.

Linus
< Previous Post in ThreadNext Post in Thread >
TopicPosted ByDate
Core 2 Errata -- problematic or overblown?Matt Sayler2007/06/27 11:39 AM
  Core 2 Errata -- problematic or overblown?anonymous2007/06/27 02:08 PM
  Core 2 Errata -- problematic or overblown?David Kanter2007/06/27 02:34 PM
    Core 2 Errata -- problematic or overblown?Joe Chang2007/06/27 03:01 PM
    Core 2 Errata -- problematic or overblown?A.T. Ho2007/06/27 04:33 PM
      Core 2 Errata -- problematic or overblown?David Kanter2007/06/27 06:31 PM
      Core 2 Errata -- problematic or overblown?Andi Kleen2007/06/28 12:35 AM
        Core 2 Errata -- problematic or overblown?anonymous2007/06/28 04:16 AM
    Core 2 Errata -- problematic or overblown?Jack A.2007/06/29 07:43 PM
      Core 2 Errata -- problematic or overblown?anon2007/07/01 10:13 AM
        AMD DocumentationDavid Kanter2007/07/01 11:03 AM
  Core 2 Errata -- problematic or overblown?Andi Kleen2007/06/27 04:02 PM
    Core 2 Errata -- problematic or overblown?Paul2007/06/27 05:06 PM
    Core 2 Errata -- problematic or overblown?Groo2007/06/28 01:10 AM
  Core 2 Errata -- problematic or overblown?Linus Torvalds2007/06/27 05:10 PM
    Core 2 Errata -- problematic or overblown?Rob Thorpe2007/06/28 01:11 AM
      Core 2 Errata -- problematic or overblown?JS2007/06/28 04:32 AM
        Core 2 Errata -- problematic or overblown?Rob Thorpe2007/06/28 05:15 AM
          Core 2 Errata -- problematic or overblown?JS2007/06/28 09:55 PM
            Core 2 Errata -- problematic or overblown?Rob Thorpe2007/06/29 12:44 AM
      Core 2 Errata -- problematic or overblown?Linus Torvalds2007/06/28 08:30 AM
        Core 2 Errata -- problematic or overblown?philt2007/06/28 04:28 PM
          Core 2 Errata -- problematic or overblown?Linus Torvalds2007/06/28 07:31 PM
            Core 2 Errata -- problematic or overblown?philt2007/06/29 01:58 AM
              Core 2 Errata -- problematic or overblown?IlleglWpns2007/06/29 02:23 AM
                Core 2 Errata -- problematic or overblown?philt2007/06/29 08:16 PM
              Core 2 Errata -- problematic or overblown?Andi Kleen2007/06/29 04:36 AM
                Core 2 Errata -- problematic or overblown?philt2007/06/29 08:09 PM
                  Core 2 Errata -- problematic or overblown?Brendan2007/06/29 11:04 PM
                    Core 2 Errata -- problematic or overblown?philt2007/06/30 01:52 AM
                      Core 2 Errata -- problematic or overblown?Brendan2007/06/30 09:25 AM
                  Core 2 Errata -- problematic or overblown?Jukka Larja2007/06/29 11:22 PM
                  Core 2 Errata -- problematic or overblown?dan2007/07/05 12:36 PM
              Core 2 Errata -- problematic or overblown?Dean Kent2007/06/29 07:31 AM
                Core 2 Errata -- problematic or overblown?philt2007/06/29 07:57 PM
                  Core 2 Errata -- problematic or overblown?Dean Kent2007/06/29 08:50 PM
                    Core 2 Errata -- problematic or overblown?philt2007/06/30 01:57 AM
                      Core 2 Errata -- problematic or overblown?Dean Kent2007/06/30 05:34 AM
                        Core 2 Errata -- problematic or overblown?philt2007/07/02 03:33 AM
                          Core 2 Errata -- problematic or overblown?Dean Kent2007/07/02 05:36 AM
                            Core 2 Errata -- problematic or overblown?philt2007/07/02 03:02 PM
                              Core 2 Errata -- problematic or overblown?JS2007/07/02 10:02 PM
                      Core 2 Errata -- problematic or overblown?David Kanter2007/07/02 03:20 PM
            Core 2 Errata -- problematic or overblown?Max2007/06/29 11:23 AM
        Core 2 Errata -- problematic or overblown?Rob Thorpe2007/06/29 06:15 AM
          Core 2 Errata -- problematic or overblown?Michael S2007/06/29 06:57 AM
    Core 2 Errata -- problematic or overblown?jozzete2007/06/29 12:54 AM
  Core 2 Errata -- problematic or overblown?Brendan2007/06/28 07:15 PM
    Core 2 Errata -- problematic or overblown?france2007/06/28 10:38 PM
  Core 2 Errata -- problematic or overblown?rwessel2007/06/29 03:20 AM
    Core 2 Errata -- problematic or overblown?jschlossel2007/06/29 10:16 AM
      Core 2 Errata -- problematic or overblown?Dean Kent2007/06/29 10:25 AM
        Core 2 Errata -- problematic or overblown?Howard Chu2007/06/30 05:09 AM
          Core 2 Errata -- problematic or overblown?JS2007/07/02 04:58 AM
      baby and bath waterrels2007/06/30 07:00 AM
      Planes, trains and cars...Anna N.2007/07/01 06:28 PM
        Planes, trains and cars...David W. Hess2007/07/01 07:40 PM
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