Date: Fri, 19 Mar 2010 07:59:56 -0400 From: John Baldwin <jhb@freebsd.org> To: Xin LI <delphij@freebsd.org> Cc: svn-src-head@freebsd.org, svn-src-all@freebsd.org, src-committers@freebsd.org Subject: Re: svn commit: r205307 - head/sys/i386/conf Message-ID: <201003190759.56385.jhb@freebsd.org> In-Reply-To: <201003190116.o2J1Gr2v094129@svn.freebsd.org> References: <201003190116.o2J1Gr2v094129@svn.freebsd.org>
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On Thursday 18 March 2010 9:16:53 pm Xin LI wrote: > Author: delphij > Date: Fri Mar 19 01:16:53 2010 > New Revision: 205307 > URL: http://svn.freebsd.org/changeset/base/205307 > > Log: > SSE is enabled by default about 5 years ago so there is no point pretending > that we support I486 and I586 CPUs in the GENERIC kernel, users wants these > support would have to build a custom kernel to explicitly disable SSE > anyways. > > MFC after: 1 month No, this is wrong. Revert this. We do _not_ unconditionally use SSE in the kernel. GENERIC should run just fine on a 486. If it doesn't, that should be fixed, but I have not seen any reports to the contrary. In general we do not use any floating-point / MMX / SSE instructions in the kernel as our FPU context-saving code doesn't support it. All the x86 world is not rack-mounted 64-bit servers. We should not remove support for non-686 CPUs for no good reason. 486 CPUs have cmpxchg and xadd so are perfectly adequate. -- John Baldwin
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