Core 2 Errata -- problematic or overblown?

By: Andi Kleen (ak-rwt.delete@this.muc.de), June 27, 2007 4:02 pm
Room: Moderated Discussions
Matt Sayler (sayler@thewalrus.org) on 6/27/07 wrote:
---------------------------
>http://marc.info/?l=openbsd-misc&m=118296441702631
>> :
>" - Basically the MMU simply does not operate as specified/implimented
>in previous generations of x86 hardware. It is not just buggy, but
>Intel has gone further and defined "new ways to handle page tables"
>(see page 58).
>- Some of these bugs are along the lines of "buffer overflow"; where
>a write-protect or non-execute bit for a page table entry is ignored.
>Others are floating point instruction non-coherencies, or memory
>corruptions -- outside of the range of permitted writing for the
>process -- running common instruction sequences."
>
>Ignore for a moment the tone, and concentrate on the substance...
>
>How significant were the TLB handling changes?

Not very -- they just clarified something which was
previously not well defined (caching of the higher
page table levels) Technically there
was a small specification/behaviour change, but
calling it a bug is probably too much -- the new behaviour is quite reasonable.

The OpenBSD quote sounds quite overblown to me, especially
trying to give it a security angle doesn't seem justified.

I'm surprised also Microsoft
just didn't add the necessary flushes to their
kernel instead of forcing Intel releasing new microcode.

Linux has the necessary flushes for quite some time
and doesn't need the new microcode.

>In general, do Core2 chips seem to be more or less buggy than previous iterations?

It's hard to say -- all CPUs have bugs and if you
try to classify them you're on shakey terrain. And
they're usually different (although sometimes multiple
cores get the same thing wrong, but that probably
says more about the ISA than the Cores)

Most bugs are obscure, but it is hard to say for sure. Also most can be worked around in the BIOS and they are found
early enough that the production BIOS actually
have the necessary workarounds.
Overall I don't have the impression that Core2 is buggier
than earlier CPUs.

>Are errata par for the course as we approach billion-transistor commodity MPUs?

Most of that is cache which rarely have errata.
And a quad core CPU is not necessarily four times
as buggy. But in general x86 CPUs are very very
well tested before they come out and very rarely
have significant bugs (and then those can be usually
worked around in the BIOS). That is why it takes so long from first samples to you actually being able to buy
the CPUs.

If you want to look for buggy CPUs you should rather
look for embedded CPUs which are often really bad.
e.g. they often ship with bugs that require compiler
workarounds which would never fly in the x86 world
and generally require OS level workarounds (which is already
very rare in the x86 world, although it happens)
Ironically they have much less transistors than the x86s.

And some other chips like graphic cards are even
worse -- since they don't have a fixed ISA they
add lots of functionality and then only use the (varying)
subset that actually ended up working in the driver.
< 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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