From owner-svn-src-all@freebsd.org Fri May 25 23:49:20 2018 Return-Path: Delivered-To: svn-src-all@mailman.ysv.freebsd.org Received: from mx1.freebsd.org (mx1.freebsd.org [IPv6:2610:1c1:1:606c::19:1]) by mailman.ysv.freebsd.org (Postfix) with ESMTP id 30209EF78A5 for ; Fri, 25 May 2018 23:49:20 +0000 (UTC) (envelope-from sobomax@sippysoft.com) Received: from mail-ot0-f194.google.com (mail-ot0-f194.google.com [74.125.82.194]) (using TLSv1.2 with cipher ECDHE-RSA-AES128-GCM-SHA256 (128/128 bits)) (Client CN "smtp.gmail.com", Issuer "Google Internet Authority G2" (verified OK)) by mx1.freebsd.org (Postfix) with ESMTPS id A1BBA79B61 for ; Fri, 25 May 2018 23:49:19 +0000 (UTC) (envelope-from sobomax@sippysoft.com) Received: by mail-ot0-f194.google.com with SMTP id t1-v6so7830348ott.13 for ; Fri, 25 May 2018 16:49:19 -0700 (PDT) X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:mime-version:references:in-reply-to:from:date :message-id:subject:to:cc; bh=/KsQ0DO5IWoHMRgJKvqj/0Li/Z5PV9Oe8fg+dNbdVxU=; b=LkKrkWyG0HiaYS1SwKmY42pDrZBY3Qv77N3tVFryH7mS/hC/9CNPWS4SLnxCaumMsT x36tHBBYzAmqDm/S1PTSUhJs8F/UBeVTLFeQDkaFiyRAv3ycbIx5B7FtB5rswu8QxzHq NE8zJfMm7PkUyDfha61Ie9IIIUoW21YWirDv6y1OMfJiA90oDLlKLfg5BfAa/ELUgKh1 HSfOx1Rq8K9I/Yfu3/1CszHaazK+zOlINE/DxRwo6nvnL7E0iewPUA6Ksk0Jd717vIrB pUo9yqmSthC3yIWvWoyAJVA3FNyhBMV+rOoUoUvQdQ4OXefxnqH96GBFPb57kCovNVai Q37Q== X-Gm-Message-State: ALKqPwe0xZ56CG+BKN1/kj2huYgyaw6kSCKxQ9L2eMWxwZGF3HMXhN+Z VawIP7pkUb6ZOlqVTqb/HNCFbKNskSUJAv6BlYKnxQ== X-Google-Smtp-Source: ADUXVKKty3ZmQvs54xJM/EouTRqrs/fIldTxxvrX9MZrPWdB9QGTvJAIW1KP7K3fIxn/vrYrjlv+j4exWlxxR51wshE= X-Received: by 2002:a9d:40ad:: with SMTP id n42-v6mr2737540ote.389.1527291724400; Fri, 25 May 2018 16:42:04 -0700 (PDT) MIME-Version: 1.0 References: <201805232218.w4NMIxMA067892@slippy.cwsent.com> <18a87d6d-14af-ef9d-80ff-403039e36692@cs.duke.edu> <20180525003949.GA710@lonesome.com> <05C5BD86-70D0-4B02-AC29-36E68B3602AE@FreeBSD.org> In-Reply-To: <05C5BD86-70D0-4B02-AC29-36E68B3602AE@FreeBSD.org> From: Maxim Sobolev Date: Fri, 25 May 2018 16:41:52 -0700 Message-ID: Subject: Re: Deorbiting i386 To: David Chisnall Cc: Mark Linimon , Matthew Macy , Andrew Gallatin , Pedro Giffuni , Cy Schubert , Brooks Davis , Eugene Grosbein , Stefan Esser , "rgrimes@freebsd.org" , Gleb Smirnoff , Sean Bruno , "svn-src-head@freebsd.org" , "svn-src-all@freebsd.org" , "src-committers@freebsd.org" X-Mailman-Approved-At: Sat, 26 May 2018 00:57:35 +0000 Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: quoted-printable X-Content-Filtered-By: Mailman/MimeDel 2.1.26 X-BeenThere: svn-src-all@freebsd.org X-Mailman-Version: 2.1.26 Precedence: list List-Id: "SVN commit messages for the entire src tree \(except for " user" and " projects" \)" List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Fri, 25 May 2018 23:49:20 -0000 That again is very subjective view, David. Sorry. Arm32 is kinda kind of the hill these days in the low-power/low cost space, but arm as a company is much more interested it seems in going into server / mobile device space rather than solidifying it's current de-facto kingdom. Those platforms based on their IP are very short lived and tightly coupled to a particular vendor with zillions busses, various kinds of weird quirks, vendor-maintained bootloaders etc. On the other hand, Intel is quickly closing the gap. If you've seen any of the atom bay trail systems in action you may understand what I mean. You get full blown x64 system with four cores and it takes only 2W of power. This is roughly equivalent of ARM8 system with a single core @ only 900MHz. So my prediction is in the 32-bit land arm will fade out as a platform and be replaced with RiscV in matter of few years and i386 will probably continue to be the platform of choice for many if Intel/Amd play that card right. -Max On Fri, May 25, 2018, 12:27 AM David Chisnall wrote: > On 25 May 2018, at 05:27, Maxim Sobolev wrote: > > > > The idea looks very inmature and short-sighted to me. i386 is here to > stay not as a server/desktop platform but as an embedded/low power/low co= st > platform for at least 5-10 years to come. There are plenty of application= s > in the world that don't need > 3gb of memory space and have no use for > extra bits (and extra silicon) to function. > > This argument seems very odd to me. If you are targeting the embedded > space, it is far easier to build a low-power chip that targets the x86-64 > ISA than the x86-32 ISA. You can move all of the 80-bit floating point > stuff into microcode. You can put anything using pair-of-32-bit-register > 64-bit operations into slow microcode. You can skimp on store forwarding > for stack addresses. You actually need fewer rename registers (one of th= e > biggest consumers of power), because x86-64 code needs to do less registe= r > juggling to fit in the architectural register space. All of these things > are big consumers of power and area and are far less necessary when runni= ng > code compiled for x86-64. You can also do tricks like the one that Intel > did on the early Atoms, where the SSE ALUs are actually only 64 bits wide > and the 128-bit ops are cracked into pairs of 64-bit micro-ops. > > As to =E2=80=98not needing more than 3GB of memory space=E2=80=99, that= =E2=80=99s what the x32 ABI > is for. This lets you get all of the advantages of the x86-64 ISA (of > which there are very many, in comparison to x86-32), without needing 64-b= it > pointers. You get the instruction density of x86-64 combined with the da= ta > density of x86-32. This is what Intel and Centaur have been pushing in t= he > embedded space for several years. > > You do pay a slight hardware cost from supporting a 48-bit virtual addres= s > space, though with superpages that=E2=80=99s negligible and the hardware = targeted > at these applications often doesn=E2=80=99t support more than a 32-bit vi= rtual > address space. > > And this completely ignores the fact that Intel has almost no presence in > the low-end embedded space. AArch32 is vastly more important there and i= f > we dropped x86-32 and shifted that effort to AArch32 then I think we=E2= =80=99d see > a lot more adoption. > > David >