Date: Fri, 28 Apr 2000 19:43:49 -0700 (PDT) From: Matthew Dillon <dillon@apollo.backplane.com> To: Brian Hechinger <BHechinger@half.com> Cc: Terry Lambert <tlambert@primenet.com>, jgowdy@home.com, smp@csn.net, jim@thehousleys.net, freebsd-smp@FreeBSD.ORG Subject: Re: RE: hlt instructions and temperature issues Message-ID: <200004290243.TAA21072@apollo.backplane.com> References: <F997095BF6F8D3119E540090276AE53015D60C@exchange01.half.com>
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:ok, bear with me here. i'm a little new to how this all works. don't know
:a whole lot about programming this deep. so i will ask questions until i
:understand. i read everything i can get my hands on, but i have a long way
:to go, and i'm sure i have questions that won't be answered there.
:
:so the whole point here is that if we continuously run instructions then we
:will burn out the CPU (or rather, run the possibility of burning out the
:CPU)?
:
:so, is this an issue purely for intel CPUs? would something like this have
:to
:be done if doing this on SPARC, motorola, Alpha, etc?
This is mainly just an issue with Intel cpu's, because intel cpu's
tend to be thrown into boxes with insufficient cooling.
Heat dissipation is a direct consequence of bit changes occuring in
logic gates in the cpu. Such bit changes are usually related to the
clock speed in one way or another, but it is often possible with
careful coding and a knowledge of how the chip was designed to construct
a sequence of instructions which yields a noticeable decrease in the
heat dissipation.
It's also possible with careful coding and a knowledge of the
chip design to construct a sequence of instructions which yields
maximum heat. Now wouldn't that be an interesting virus! :-) :-)
Personally speaking I don't think it's a legitimate issue. I certainly
would oppose anybody trying to commit complex code to make HLT work for
SMP at least not before trying out simpler solutions.
-Matt
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