Date: Sat, 29 Apr 2000 01:31:41 +0000 (GMT)
From: Terry Lambert <tlambert@primenet.com>
To: BHechinger@half.com (Brian Hechinger)
Cc: dillon@apollo.backplane.com ('Matthew Dillon'), tlambert@primenet.com (Terry Lambert), jgowdy@home.com, smp@csn.net, jim@thehousleys.net, freebsd-smp@FreeBSD.ORG
Subject: Re: hlt instructions and temperature issues
Message-ID: <200004290131.SAA12025@usr08.primenet.com>
In-Reply-To: <F997095BF6F8D3119E540090276AE53015D60C@exchange01.half.com> from "Brian Hechinger" at Apr 28, 2000 08:23:55 PM
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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)? No. The point is that the CPUs run hotter, which means shorter batter life, more power consumption, higher cooling requirements, and limitations on installtion in close space, as a result. > 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? It's a small win for most applications, and a big win for some. The win applies to all processors, where you can do a halt in an idle loop and IPI or interrupt back to life. > aprox how much time (percentage) is being spent cooling the > CPU? It's in "not heating the CPU". If done correctly, there's about a six instruction latency overall, counting the code in the scheduler and the halt and wakeup overhead. This will vary from processor to processor, based on the voodoo necessary to make it work. > would there be a significant increase in speed if we could > avoid this? Hotter processors run fractionally slower. All in all, it's about a wash, in terms of processor effectiveness. The real wins are heat dissipation and power consumption. > also, is heat measured and we act apropriately, or do we just > cool enough to ensure that we don't have a chance to heat up > too far? It's not an active "cooling". I guess if you had chip temeperature detection code and ran the cpu only so long as it was below a certain temperature, and when it hit it, you didn't run it until it was some ways below that temeperature, we could get the overclocking weenies machines to work stablely. I suspect their overall performance would end up being less than what it would have been, had they not been overclocking... Just think... no more "my machine is doing wierd behaviour X!" and "Are you overclocking your CPU?" type exchanges, ever again. 8-) 8-) 8-). Terry Lambert terry@lambert.org --- Any opinions in this posting are my own and not those of my present or previous employers. To Unsubscribe: send mail to majordomo@FreeBSD.org with "unsubscribe freebsd-smp" in the body of the message
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