Messages in this thread | | | From | Arnd Bergmann <> | Date | Thu, 8 Feb 2018 22:57:36 +0100 | Subject | Re: [BUG] x86 : i486 reporting to be vulnerable to Meltdown/Spectre_V1/Spectre_V2 |
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On Thu, Feb 8, 2018 at 10:16 PM, Alan Cox <gnomes@lxorguk.ukuu.org.uk> wrote: > On Thu, 8 Feb 2018 16:22:40 +0100 > Arnd Bergmann <arnd@arndb.de> wrote: > >> On Thu, Feb 8, 2018 at 2:49 PM, Alan Cox <gnomes@lxorguk.ukuu.org.uk> wrote: >> >> What about Pentium II and 3? I'm using 5 such machines (and also a Pentium >> >> MMX). I've tried a spectre test before and it wasn't reading anything useful. >> >> Don't know about meltdown. Is there a complete test program? (The web is so >> >> full of crap that even google can't find anything useful.) >> > >> > For x86 speculation came in (as far as I can tell) in >> > >> > AMD Am5x86 >> > Cyrix 5x86, but branch predictors are disabled by default according to >> > the docs >> > Cyrix 6x86, branch prediction on by default >> > Pentium Pro >> > >> > There are later processors that don't have speculation: Quark series, Nat >> > Semi/Cyrix Geode, earliest AMD geode (I think), some Intel Atom >> > processors. >> >> Wasn't Am5x86 just a 486 clone? AFAICT, speculation only came with the >> K6 (Am6x86 aka NexGen Nx6x86) > > The AMD 486 was a 486, just like UMC. The Am5x86 was a sort of super 486. > But you are correct I'm muddling that with the K5 - which does speculate > or at least some of them do. The K5 branch predictor is software > controllable via the HWCR MSR but who has one today to test or cares 8)
Right, I completely forgot about the K5.
>> All the Geode are apparently derived from Cyrix 5x86 (I always thought > > Not quite all. The older ones are Cyrix 5x86 related which indeed means > they don't have branch prediction on by default until the LX. Just to > confuse the AMD Geode NX is basically an Athlon mobile.
This one I knew, I was just not using precise enough language.
Arnd
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