From mboxrd@z Thu Jan 1 00:00:00 1970 From: Scott Robert Ladd Subject: Re: Hyper-threading Date: Mon, 02 Jun 2003 12:29:55 -0400 Sender: linux-smp-owner@vger.kernel.org Message-ID: <3EDB7B83.1020108@coyotegulch.com> References: Mime-Version: 1.0 Content-Transfer-Encoding: 7bit Return-path: In-Reply-To: List-Id: Content-Type: text/plain; charset="us-ascii"; format="flowed" To: Mike Dresser Cc: linux-kernel@vger.kernel.org, linux-smp@vger.kernel.org Mike Dresser wrote: > Indeed, I saw that. On the P4 2.66ghz that you have, the "second" cpu is > disabled by intel, as they sell hyperthreading only on the newer Xeon P4 > (which you don't have), and the new 800FSB (4x200) units, which again > you don't have. > > ..... CPU clock speed is 2672.7802 MHz. > ..... host bus clock speed is 133.6388 MHz. Some Pentium 4 chips support HT even when they officially "don't". For example, my system has an Intel MB and a Pentium 4 2.8GHz processor; it boots using HT just fine. From a recent boot: Tycho kernel: CPU1: Intel Pentium 4 (Northwood) stepping 07 Tycho kernel: Total of 2 processors activated (11042.81 BogoMIPS). Tycho kernel: cpu_sibling_map[0] = 1 Tycho kernel: cpu_sibling_map[1] = 0 Tycho kernel: ENABLING IO-APIC IRQs Tycho kernel: Setting 2 in the phys_id_present_map Tycho kernel: ...changing IO-APIC physical APIC ID to 2 ... ok. Tycho kernel: ..TIMER: vector=0x31 pin1=2 pin2=0 Tycho kernel: testing the IO APIC....................... Tycho kernel: .................................... done. Tycho kernel: Using local APIC timer interrupts. Tycho kernel: calibrating APIC timer ... Tycho kernel: ..... CPU clock speed is 2783.0819 MHz. Tycho kernel: ..... host bus clock speed is 132.0562 MHz. Tycho kernel: checking TSC synchronization across 2 CPUs: passed. Tycho kernel: Starting migration thread for cpu 0 Tycho kernel: Bringing up 1 Tycho kernel: CPU 1 IS NOW UP! Tycho kernel: Starting migration thread for cpu 1 Tycho kernel: CPUS done 2 Note the "132.0562" MHz bus speed. I obtained my system directly from Intel; however, I know of a few people who obtained Pentium 4 chips from retailers, and their processors support HT with a 4x133 bus. -- Scott Robert Ladd Coyote Gulch Productions (http://www.coyotegulch.com) Professional programming for science and engineering; Interesting and unusual bits of very free code.