Date: Tue, 17 Apr 2001 17:46:29 -0700 (PDT) From: Linh Pham <lplist@closedsrc.org> To: Jeremiah Gowdy <jgowdy@home.com> Cc: Vincent Poy <vince@oahu.WURLDLINK.NET>, Kris Kennaway <kris@obsecurity.org>, Marc W <mwlist@lanfear.com>, Kyle <freebsd@sysmach.com>, <questions@FreeBSD.ORG> Subject: Re: the AMD factor in FreeBSD Message-ID: <Pine.BSF.4.33.0104171735110.45373-100000@q.closedsrc.org> In-Reply-To: <002c01c0c795$15bee360$015778d8@sherline.net>
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On 2001-04-17, Jeremiah Gowdy scribbled: # This is not entirely true. Although the P4 has a 400mhz bus speed, actual # testing shows that the Pentium 4 puts out almost the same throughput as it's # 100/133mhz counterparts, it simply takes more clocks to do so. The # applications in which the Pentium 4 wins are SSE/SSE2 optimized. These are # not all that common. If you're referring to MPEG-4 encoding as tested in # Tom's Hardware, remember that the Pentium 4 got the crap kicked out of it in # the non-SSE2 non-3DNow! optimized version of the test, and since the # application wouldn't even BE SSE2 optimized if it weren't for Intel not # liking the results of the benchmark, I don't really care much for the Intel # optimized benchmark. If Intel were going to go around and optimize # EVERYONE's software, that would be another story. I forgot to include the note about SSE2... thanks for mentioning that :) The Pentium 4 does suffer from not only a crippled architecture but also from the higher memory access latency, thanks to DRDRAM. The longer pipeline affects the core speed, not the bus side (or, at least not directly). The longer the pipeline, the clock rate must be higher to run at the same speed as a processor with a lower clock rate and a shorter pipeline. The reason why the Pentium 4 has a 100Mhz QDR (quad data rate) FSB is to match the bandwidth of the dual Rambus memory channel architecture... not because the pipeline is longer. # Not to mention the fact that the Pentium 4 clocks down as the processor # heats up, causing a Pentium 4 1.5ghz to run at 750 mhz when the load is 100% # (1.0) for an extended period of time. No wonder the Pentium 4 1.5 ghz loses # head to head with an Athlon 1.2 ghz in non-Intel optimized testing. The # processor speed steps like a laptop depending on the power/heat conditions. # Even calling such a cpu a 1.5 ghz is a stretch in my opinion with that # underclocking. The P4 will run at 1.5 ghz when idle, but then clock down to # 750 mhz when the load is 1.0. What the heck is the point of that ?! It's # more than happy to burn away power idling at 1.5 ghz, but when the processor # is actually needed to get some work done, it has to underclock to avoid # overheating. "1.5 ghz, except when you need it." # # http://slashdot.org/article.pl?sid=01/04/13/2041238&mode=thread # http://www.inqst.com/articles/p4bandwidth/p4bandwidthmain.htm Kyle from HardOCP posted on Sunday 04.15.2001 refuting the article that was written about the Pentium 4 throttling down. There isn't a direct link to Kyle's note, but you can find it at http://hardocp.com. According to Kyle, the throttling option can be enabled/disabled from within the BIOS setup and that the processor shouldn't be throttling at all if there is proper cooling. # 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. AMD cpus support up to 14 way SMP. The PIII can only support 2 # cpus, and the Xeon can only support 4. http://www.sandpile.org The new Paliminos and the new C-series Athlons run on a 133Mhz DDR FSB, not at 100Mhz, but I think the 760MP chipset does (officially or unofficially, I don't know) support 100Mhz DDR FSB. -- Linh Pham [lplist@closedsrc.org] // 404b - Brain not found To Unsubscribe: send mail to majordomo@FreeBSD.org with "unsubscribe freebsd-questions" in the body of the message
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