Date: Wed, 22 May 2002 11:58:12 -0700 From: Brooks Davis <brooks@one-eyed-alien.net> To: Terry Lambert <tlambert2@mindspring.com> Cc: Alfred Perlstein <bright@mu.org>, "Dorr H. Clark" <dclark@applmath.scu.edu>, freebsd-smp@freebsd.org Subject: Re: hyperthreading: myth or legend? (was Re: hyperthreading? (was Re: question)) Message-ID: <20020522115812.A7330@Odin.AC.HMC.Edu> In-Reply-To: <3CEBE6FD.626DC5DD@mindspring.com>; from tlambert2@mindspring.com on Wed, May 22, 2002 at 11:44:13AM -0700 References: <20020514222840.GB1585@elvis.mu.org> <Pine.GHP.4.21.0205220940410.28331-100000@hpux38.dc.engr.scu.edu> <20020522172759.GV54960@elvis.mu.org> <3CEBE6FD.626DC5DD@mindspring.com>
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--nFreZHaLTZJo0R7j Content-Type: text/plain; charset=us-ascii Content-Disposition: inline Content-Transfer-Encoding: quoted-printable On Wed, May 22, 2002 at 11:44:13AM -0700, Terry Lambert wrote: > According to the Intel documentation I read, hyperthreading is not > the same thing as simply having the extra CPUs on the same die (which > is what you seem to be implying it is). You're both right. Optimal performance is achieved by optimizing the way Terry described, at that's a direction we need to consider assuming hyperthreading stays around, however, when you don't do any of those things, Intel lets you pretend you have two CPUs on one die. Performance is not identical (if nothing else the two CPUs share memory bandwidth and the P4 is seriously bandwidth hungry), but it just works. When you think about it, Intel had to go with that approach for all the reasions AMD emulates the Intel SMP programming model on the Athlon. Simply put, they have to support NT 4, Win2K, and XP without modification. Heck, I'd be slightly suprised if Windows.net supports Hyperthreading nativly. Of course, since they show up as two CPUs each, you can't run NT Server on a dual Xeon box and I think you need Datacenter for a quad so it's not nearly as much of a win for Windows users. :-) -- Brooks --=20 Any statement of the form "X is the one, true Y" is FALSE. PGP fingerprint 655D 519C 26A7 82E7 2529 9BF0 5D8E 8BE9 F238 1AD4 --nFreZHaLTZJo0R7j Content-Type: application/pgp-signature Content-Disposition: inline -----BEGIN PGP SIGNATURE----- Version: GnuPG v1.0.6 (GNU/Linux) Comment: For info see http://www.gnupg.org iD8DBQE86+pDXY6L6fI4GtQRAgUSAJwOdwqWBKlRgyIUYzkqLL6YktOEKQCgkN0H 0xdwZdht0CpwE8UAaG3TZOw= =syvB -----END PGP SIGNATURE----- --nFreZHaLTZJo0R7j-- To Unsubscribe: send mail to majordomo@FreeBSD.org with "unsubscribe freebsd-smp" in the body of the message
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