From mboxrd@z Thu Jan 1 00:00:00 1970 From: "Robert G. Brown" Date: Mon, 13 Jul 1998 17:04:22 +0000 Subject: Re: Ultra AXmp Message-Id: List-Id: References: In-Reply-To: MIME-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit To: ultralinux@vger.kernel.org On Mon, 13 Jul 1998, Matthew Jacob wrote: > > > but the memory interconnect is always the sticky wicket on SMP machines, > > although for the PC, we simply dribble along at (now) 100mhz. :) > > Umm.. I thought that the new PC motherboards coming out are running > at 400Mhz (no, not CPU speed- I mean internal bus speed...) The current 440BX systems have a 100 MHz memory bus (50% faster than the old PPro/PII bus but still slower than one would like). As I learned very forcefully recently, their cache speed is half the CPU clock, so a 400 MHz CPU has a cache running at 200 MHz, making it finally the equal or superior of the PPro in every respect. The motherboards support PC-100 SDRAM, which is measurably faster in than EDO in some applications -- but your milage will very much depend upon your application -- its size (does it fit in cache), its locality (does it cache thrash bytewise or read streaming sequences of data) and the like. Unless you are running jobs more than a few MB in size (including data) you will, frankly, probably not see much advantage in the SDRAM memory or the memory clock, but folks doing large matrix multiplies and the like have reported significant speedup and considerably better SMP scaling of memory access times. Now, there are a whole slew of things purported to be coming down the pipe from Intel this fall starting with 450MHz processors, and (as I recall) we should see "Merced" (their next generation CPU and system) sometime next year. In merced I believe we'll see some very significant capacity/speed upgrades in lots of venues -- you might check out the Intel website to see what they say. rgb Robert G. Brown http://www.phy.duke.edu/~rgb/ Duke University Dept. of Physics, Box 90305 Durham, N.C. 27708-0305 Phone: 1-919-660-2567 Fax: 919-660-2525 email:rgb@phy.duke.edu