Date: Sun, 9 Nov 1997 16:59:16 -0500 (EST) From: "John S. Dyson" <toor@dyson.iquest.net> To: nate@mt.sri.com (Nate Williams) Cc: perlsta@cs.sunyit.edu, gpalmer@freebsd.org, freebsd-smp@freebsd.org Subject: Re: Best processor? Message-ID: <199711092159.QAA27125@dyson.iquest.net> In-Reply-To: <199711092131.OAA05995@rocky.mt.sri.com> from Nate Williams at "Nov 9, 97 02:31:45 pm"
next in thread | previous in thread | raw e-mail | index | archive | help
Nate Williams said: > > dual 300mhz PIIs will beat dual PPro 200mhz > > >From the noise I've been hearing lately on the mailing lists, this > suprises me. Do you have #'s to back it up? > I am not responding with numbers, but if you look at it, it is likely true: 1) The PIIs have 512K cache, while the PPro has (normally) 256K cache. Therefore bus utilization is likely less with the PII. Even in the case of a 512K cache, the bus utilization is going to be nearly the same. In a DP system, bus utilization is likely less important than in 4-way systems anyway. 2) Expect about 3-5% miss rate with an 8K or 16K 1st level cache. (I have really measured it on real applications.) Miss rate can be much lower than that though. The miss rate does not scale linearly downward with 1st level cache size, but it does go down (especially with n-way associative cache schemes.) 3) Single processor PIIs at 300MHz are almost always (if not always) faster than a PPro at 200MHz running real code. PII MB's can support SDRAM now, and that really does help mitigate the aggregate performance loss due to the 1/2 speed 2nd level cache. If you are talking about 233MHz PII processors vs. 200MHz PPro processors, it is harder to decide on which processor is faster, but I do think that the PII will win out on average. Clock your PPro at 233MHz, and the PPro will win out, except for MMX type apps, or on memory intensive apps, where the LX chipset and SDRAM memory speeds help. The huge gotcha in all of this is that the PII only caches the first 512MB of memory. -- John dyson@freebsd.org jdyson@nc.com
Want to link to this message? Use this URL: <https://mail-archive.FreeBSD.org/cgi/mid.cgi?199711092159.QAA27125>