Date: Thu, 1 Apr 2004 15:11:38 +1000 (EST) From: Bruce Evans <bde@zeta.org.au> To: John Baldwin <john@baldwin.cx> Cc: Dag-Erling =?iso-8859-1?q?Sm=F8rgrav?= <des@des.no> Subject: Re: CFD: XMLification of NOTES Message-ID: <20040401145536.A5418@gamplex.bde.org> In-Reply-To: <200403311105.19088.john@baldwin.cx> References: <20040328094048.GA40406@phantom.cris.net> <20040330232429.GA65170@phantom.cris.net> <xzpn05xq4bh.fsf@dwp.des.no> <200403311105.19088.john@baldwin.cx>
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On Wed, 31 Mar 2004, John Baldwin wrote: > On Tuesday 30 March 2004 06:54 pm, Dag-Erling Sm=F8rgrav wrote: > > CPU_I386 should not conflict with SMP, but a kernel build with both > > will be very slow. > > No, it does conflict. There's no cmpxchg on i386 and no one has had the > desire or time to emulate one for 386 machines. Doing so would be a wast= e in > my opinion as well. des only claimed that it "should not". Emulating cmpxchg might make a kernel built with both slow, but the current CPU_I386 only adds a tiny amount of slowness. It just doesn't work on multi-CPU systems if multiple CPUs are actually used. Does it actually conflict in practice (except for the forced #error) if the hardware is UP? jhb's APIC changes made configuring with SMP not require APIC, so SMP kernels work on UP systems. Configuring with I386_CPU shouldn't affect this, but it does because of the forced #error at compile time. Bruce
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