On Thu, Feb 8, 2018 at 2:49 PM, Alan Cox <gno...@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) All the Geode are apparently derived from Cyrix 5x86 (I always thought it was a 6x86, but the internet disagrees). For Geode GX, a specification update at  mentions a special procedure for enabling branch prediction, Geode LX apparently gets this right and always has branch prediction. > The more obscure ones - the Transmeta apparently may, the IDT Winchip > documentation strongly implies it doesn't The Winchip is what eventually turned into the VIA Nano, which does have speculative execution, but I don't think the earlier C3 and C7 did, they are much closer to the original Winchip design. Arnd  http://support.amd.com/TechDocs/31533E_gx_2.1_specupdate.pdf