Date: Wed, 18 Apr 2001 05:07:32 -0500 From: Mike Meyer <mwm@mired.org> To: "Jeremiah Gowdy" <jgowdy@home.com> Cc: questions@freebsd.org Subject: Re: the AMD factor in FreeBSD Message-ID: <15069.26468.279995.42083@guru.mired.org> In-Reply-To: <64762482@toto.iv>
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Jeremiah Gowdy <jgowdy@home.com> types: > As for the AMD+SMP vs Intel+SMP, I can't say regarding the FreeBSD support, > however, AMD's SMP is supposed to be far faster than Intel's because it has > a Point-to-Point bus for the SMP connection, meaning _each_ CPU has a > dedicated 200mhz (100mhz DDR) connection to the bus, when on an Intel SMP > motherboard the two or more cpus will share the same 100mhz bus. That means > on a 4 way SMP Intel system, each cpu will get an effective 25mhz access to > the bus under full load in theory. By the same theory, AMD cpus would each > have their own 200mhz dedicated connection to the bus, even in an 8 cpu > setup. You're talking about the speed of the connection to the bus, without talking about the speed of the bus. If the bus in question is 100MHz, then in any 4-cpu system at full load, each cpu will have at most 25MHz on the bus, never mind that their connection to the bus is 200MHz. So you've just spent 4 times the amount on cpu bus hardware for no gain in performance. If the bus is 133MHz, then each cpu can get 33MHz on the bus on a loaded system, and the shared connection to the bus causes a problem. There may be something obvious I've overlooked - in which case, I'm sure I'll be told about it. <mike -- Mike Meyer <mwm@mired.org> http://www.mired.org/home/mwm/ Independent WWW/Perforce/FreeBSD/Unix consultant, email for more information. To Unsubscribe: send mail to majordomo@FreeBSD.org with "unsubscribe freebsd-questions" in the body of the message
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