From owner-freebsd-amd64@FreeBSD.ORG Fri Mar 12 12:00:19 2004 Return-Path: Delivered-To: freebsd-amd64@freebsd.org Received: from mx1.FreeBSD.org (mx1.freebsd.org [216.136.204.125]) by hub.freebsd.org (Postfix) with ESMTP id 50F8516A4CE for ; Fri, 12 Mar 2004 12:00:19 -0800 (PST) Received: from odin.ac.hmc.edu (Odin.AC.HMC.Edu [134.173.32.75]) by mx1.FreeBSD.org (Postfix) with ESMTP id 373EC43D1F for ; Fri, 12 Mar 2004 12:00:19 -0800 (PST) (envelope-from brdavis@odin.ac.hmc.edu) Received: from odin.ac.hmc.edu (IDENT:brdavis@localhost.localdomain [127.0.0.1]) by odin.ac.hmc.edu (8.12.10/8.12.3) with ESMTP id i2CK00aN001798; Fri, 12 Mar 2004 12:00:03 -0800 Received: (from brdavis@localhost) by odin.ac.hmc.edu (8.12.10/8.12.3/Submit) id i2CJxxpw001776; Fri, 12 Mar 2004 11:59:59 -0800 Date: Fri, 12 Mar 2004 11:59:59 -0800 From: Brooks Davis To: Jem Matzan Message-ID: <20040312195958.GA32345@Odin.AC.HMC.Edu> References: <200403121301.i2CD1oQC076505@lurza.secnetix.de> <4051B7D3.8020404@thejemreport.com> <20040312174736.GD7661@Odin.AC.HMC.Edu> <4052130E.9060601@thejemreport.com> Mime-Version: 1.0 Content-Type: multipart/signed; micalg=pgp-sha1; protocol="application/pgp-signature"; boundary="gKMricLos+KVdGMg" Content-Disposition: inline In-Reply-To: <4052130E.9060601@thejemreport.com> User-Agent: Mutt/1.5.4i X-Virus-Scanned: by amavisd-milter (http://amavis.org/) on odin.ac.hmc.edu cc: freebsd-amd64@freebsd.org Subject: Re: Peer review of AMD64/FreeBSD article X-BeenThere: freebsd-amd64@freebsd.org X-Mailman-Version: 2.1.1 Precedence: list List-Id: Porting FreeBSD to the AMD64 platform List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Fri, 12 Mar 2004 20:00:19 -0000 --gKMricLos+KVdGMg Content-Type: text/plain; charset=us-ascii Content-Disposition: inline Content-Transfer-Encoding: quoted-printable On Fri, Mar 12, 2004 at 02:44:14PM -0500, Jem Matzan wrote: > Brooks Davis wrote: >=20 > >On Fri, Mar 12, 2004 at 08:14:59AM -0500, Jem Matzan wrote: > >=20 > > > >>Hyper-Threading seemed to help with processes that didn't require a=20 > >>heavy CPU load. The OpenSSL tests show it being markedly faster in the= =20 > >>smaller algorithms, but lagging way behind the 64-bit Athlon64 when the= =20 > >>serious number crunching comes into play. Intel's press kit shows HT=20 > >>(and SSE3) giving an advantage when multitasking with four desktop=20 > >>programs in Windows XP. It's just too hard to show that reliably though= =2E=20 > >>There's a lot of anecdotal evidence to suggest that AMD64 is faster on= =20 > >>the desktop (in X) in 64-bit mode than the Prescott is in 32-bit, but= =20 > >>I'm having trouble proving it. > >> =20 > >> > > > >I think it would be a mistake to assume the HT is what accounts for > >the performance difference. There are so many other architectural > >differences it's hard to see how you could isolate the effects of > >HT. My suspicition is that better performance on small=20 > >algorithms is due to them being more or less memory bound (and thus > >similar to the pure synthetic benchmarks). > > > By comparing the Pentium4 to the Athlon64 in i386 mode, you can better=20 > see the advantage of HT Technology. This is especially evident in the=20 > OpenSSL tests. I strongly disagree. All you can see is that they differ. The architectural differences between P4 CPUs and current generation amd64 CPUs are a whole lot more then HT. You've got a different memory memory system, vastly different pipeline lengths, etc. For that matter, on paper at least, I wouldn't expect HT to help much if any in this situation since you're not trying to do two things at once. -- 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 --gKMricLos+KVdGMg Content-Type: application/pgp-signature Content-Disposition: inline -----BEGIN PGP SIGNATURE----- Version: GnuPG v1.2.1 (GNU/Linux) iD8DBQFAUha9XY6L6fI4GtQRAokIAKCycB2+Tzi3ArakGZCGqThmJ25MLQCdHpdR jKUiWEUi00s/FRIDbShYIYY= =99Tq -----END PGP SIGNATURE----- --gKMricLos+KVdGMg--