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Date:      Tue, 11 Jan 2005 22:18:27 -0500
From:      Chuck Swiger <cswiger@mac.com>
To:        David Kelly <dkelly@HiWAAY.net>
Cc:        freebsd-questions@freebsd.org
Subject:   Re: Hyperthreading hurts 5.3?
Message-ID:  <41E49703.2030209@mac.com>
In-Reply-To: <0D509666-643F-11D9-A9EF-000393BB56F2@HiWAAY.net>
References:  <9094-SnapperMsgD246FC56BE0A255B@68.243.126.247> <0D509666-643F-11D9-A9EF-000393BB56F2@HiWAAY.net>

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David Kelly wrote:
>> (disabling HT will apparently mean I have to reinstall XP on the other
>> drive.
> 
> What does XP have to do with it? IIRC on Dell its F2 during the power-on 
> diagnostics to reach the built-in BIOS config. That is where HT is to be 
> disabled.

If you install and configure many flavors of Windows on a SMP system, that 
installation will not work if you move that image to a uni-proc system by 
swapping disks or otherwise removing CPU's (ie, by turning off HT'ing).  I 
last saw this with a Win2K system, which immediately blue-screened with an 
"invalid SMP HAL" error very early in the boot.

[ It doesn't surprise me that one would want or have to reinstall XP after 
disabling HyperThreading.  There exist even less comprehensible reasons which 
oblige people to reinstall Windows.... ]

-- 
-Chuck



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