linux-kernel - Intel Core Duo/Duo2 T2300/E6400 - Hyper-Threading (the absence of)

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Message-ID: <20070108094432.GF5276@curie-int.orbis-terrarum.net>
Date:	Mon, 8 Jan 2007 01:44:32 -0800
From:	"Robin H. Johnson" <robbat2@...too.org>
To:	linux-kernel@...r.kernel.org
Subject: Intel Core Duo/Duo2 T2300/E6400 - Hyper-Threading (the absence of)

(Please CC me, I am not subscribed to LKML [I have set the
Mail-Followup-To header accordingly]).

On two of my new machines, with Intel Core Duo T2300 and Core2 Duo E6400
chips respectively, I noticed some weirdness in how many CPUs are
present. 

If the hyper-threading bit is present in the CPU info, should there
always be a an extra CPU presented to the system per physical core?

Both the Core1 and Core2 chips I have the ht bit set, but present only
their two physical cores to the system. No access to the hyper-threading
capabilities at all. I also see no configuration options in the BIOS to
enable or disable hyper-threading. That is, /proc/cpuinfo and all
topology data only shows 2 CPUs present, and that they are not the HT
pair.
(CONFIG_NR_CPUS=8 is set).

(This was originally triggered by somebody else's code that read the CPU
flags, saw hyper-threading, and decided there were 2x cpus for each
physical core. Said code has already been taken out back and shot
repeatedly).

-- 
Robin Hugh Johnson
Gentoo Linux Developer
E-Mail     : robbat2@...too.org
GnuPG FP   : 11AC BA4F 4778 E3F6 E4ED  F38E B27B 944E 3488 4E85

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