Date: Sat, 04 Mar 2017 14:51:50 -0800 From: John Baldwin <jhb@freebsd.org> To: Pedro Giffuni <pfg@freebsd.org> Cc: Slawa Olhovchenkov <slw@zxy.spb.ru>, src-committers@freebsd.org, svn-src-all@freebsd.org, svn-src-head@freebsd.org Subject: Re: svn commit: r314669 - head/sys/i386/conf Message-ID: <7873439.f6BlOXHt6g@ralph.baldwin.cx> In-Reply-To: <D81029FA-61CF-4648-A2A8-8570DEF28B14@FreeBSD.org> References: <201703041504.v24F4HMh023937@repo.freebsd.org> <2368011.hGEX4V32U5@ralph.baldwin.cx> <D81029FA-61CF-4648-A2A8-8570DEF28B14@FreeBSD.org>
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On Saturday, March 04, 2017 03:49:52 PM Pedro Giffuni wrote: >=20 > > Il giorno 04 mar 2017, alle ore 14:43, John Baldwin <jhb@freebsd.or= g> ha scritto: > >=20 > > On Saturday, March 04, 2017 10:52:46 AM Pedro Giffuni wrote: > >>=20 > >> On 03/04/17 10:32, Slawa Olhovchenkov wrote: > >>> On Sat, Mar 04, 2017 at 03:04:17PM +0000, Pedro F. Giffuni wrote:= > >>>=20 > >>>> Author: pfg > >>>> Date: Sat Mar 4 15:04:17 2017 > >>>> New Revision: 314669 > >>>> URL: https://svnweb.freebsd.org/changeset/base/314669 > >>>>=20 > >>>> Log: > >>>> Drop i486 from the default i386 GENERIC kernel configuration. > >>>>=20 > >>>> 80486 production was stopped by Intel on September 2007. Droppi= ng the 486 > >>>> configuration option from the GENERIC kernel improves performan= ce > >>>> slightly. > >>>>=20 > >>>> Removing I486_CPU is consistent at this time: we don't support = any > >>>> processor without a FPU and the PC-98 arch, which frequently in= volved i486 > >>>> CPUs, is also gone so we don't test such platforms anymore. > >>>=20 > >>> What is realy mean? > >>=20 > >> This means we don't do work-arounds that would be required for raw= 486. > >> Instead we will use the 586 instructions by default. > >=20 > > This doesn't change that. The kernel already has runtime tests in = place > > for new things on 486 and later via cpuid. > >=20 >=20 > Hmm ..then I am wondering if I effectively changed anything? The only change is a 486 now panics on boot when it used to work fine. = :-/ Nothing for other CPUs has changed. =20 > The number came out from an old posting involving buildworld times, w= hich I can=E2=80=99t find now :(. > Things seem to have changed a lot: it was surely using GCC back then,= I don=E2=80=99t believe clang does much distinction about 486 at all. >=20 > BTW, does it make sense to keep i586 in the configuration still? Both= i486 and i586 were once removed but later re-instated in r205336. If anything I'd probably say we should do what bde@ suggested and just remove CPU class entirely (and act as if 486, 586, and 686 are always defined). --=20 John Baldwin
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