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Date:      Mon, 01 May 2000 10:11:40 -0700
From:      Peter Wemm <peter@netplex.com.au>
To:        Karl Pielorz <kpielorz@tdx.co.uk>
Cc:        djb@ifa.au.dk, Steve Passe <smp@csn.net>, smp@FreeBSD.ORG
Subject:   Re: hlt instructions and temperature issues 
Message-ID:  <20000501171141.04ADF1CD7@overcee.netplex.com.au>
In-Reply-To: Message from Karl Pielorz <kpielorz@tdx.co.uk>  of "Sun, 30 Apr 2000 15:21:57 BST." <390C4185.5C07088A@tdx.co.uk> 

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Karl Pielorz wrote:
> > I personally wouldn't worry about 5% performance difference, and go for the
> > lower temperature and increased stability. But others may have different
> > opinions. My proposal is therefore to make the hlt instruction a kernel
> > option for SMP systems. That way everyone can experiment for themselves and
> > possible problems may be detected.
> 
> Everyone,
> 
> This thread has been a fascinating walk through CPU temperatures under SMP -
> but surely, no one should be designing a system that relies on the 'thermal
> characteristics of the software running' to ensure safe operation? - If the
> spec says you need to dissipate 32 Watts of heat from the CPU, you design a
> system to dissipate 32 Watts (probably a bit more for 'safety'? :)...
> 
> Taking it to an extreme, it would be like building a system that falls over
> when it 'happens to be busy' one day, 'cause someone ran something
> computationally intensive? - I know for a fact these systems do exist, but we
> don't really want to be helping sweep the cause under the rug do we?

For example, run a rc5des or something and see how good your heat
dissipation is.  It makes my laptop cooling system go berzerk, and makes
the cpus run even hotter than the present idle loop under SMP.

Cheers,
-Peter



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