Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S262525AbTFKPuy (ORCPT ); Wed, 11 Jun 2003 11:50:54 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S262562AbTFKPuy (ORCPT ); Wed, 11 Jun 2003 11:50:54 -0400 Received: from wmail.atlantic.net ([209.208.0.84]:10720 "HELO wmail.atlantic.net") by vger.kernel.org with SMTP id S262525AbTFKPuw (ORCPT ); Wed, 11 Jun 2003 11:50:52 -0400 Message-ID: <3EE7561C.9010202@techsource.com> Date: Wed, 11 Jun 2003 12:17:32 -0400 From: Timothy Miller User-Agent: Mozilla/5.0 (X11; U; Linux i686; en-US; rv:1.0.1) Gecko/20020823 Netscape/7.0 X-Accept-Language: en-us, en MIME-Version: 1.0 To: mikpe@csd.uu.se CC: Steven Cole , Alan Cox , Samuel Flory , John Appleby , xyko_ig@ig.com.br, Linux Kernel Mailing List Subject: Re: Wrong number of cpus detected/reported References: <434747C01D5AC443809D5FC540501131569E@bobcat.unickz.com> <3EE64161.5010102@rackable.com> <1055279041.2270.42.camel@spc9.esa.lanl.gov> <1055280955.32661.35.camel@dhcp22.swansea.linux.org.uk> <1055281927.2269.47.camel@spc9.esa.lanl.gov> <16102.22713.50999.54138@gargle.gargle.HOWL> Content-Type: text/plain; charset=us-ascii; format=flowed Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1393 Lines: 35 mikpe@csd.uu.se wrote: > Steven Cole writes: > > On Tue, 2003-06-10 at 15:35, Alan Cox wrote: > > > > wp : yes > > > > flags : fpu vme de pse tsc msr pae mce cx8 apic sep mtrr mca cmov pat pse36 clflush dts acpi mmx fxsr sse sse2 ss ht tm > > > > bogomips : 2798.38 > > > > > > > > See that ht flag near the end? > > > > > > The ht flag means the ht facilities (mtrr etc) are present, doesnt mean > > > HT necessarily is > > > > Is there a reliable method, apart from knowing 'a priori' the mapping > > from CPU models and stepping to hyperthreading capability? > > Yes. Execute cpuid with eax=1 on each CPU. ebx describes among other things > the number of threads and which thread you're on. If you ever find yourself > on a non-zero thread, you have HT. I presume, however, that to get into a non-zero thread, you have to turn HT on. That is, when the machine first powers up, there is nothing for the second thread to execute, so it's turned off. (I'm assuming something similar for SMP boxes.) So, the real question should be, before you attempt to turn on HT, how do you find out whether or you CAN turn on HT. - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/