On Mon, Feb 23, 2009 at 5:27 AM, Mark Hahn <h...@mcmaster.ca> wrote: > AMD Opteron "Shangai" 6MB L3 : 90% of peak >> Intel "Nehalem" Core i7 : 95.2% of peak >> Intel Itanium 2 : 95.6% of peak >> > > interesting numbers, and Goto's efforts are always respected. > it would be valuable to understand why, though. I usually think > of ia64 as being basically designed specifically to make this kind of > hero-optimization possible. but I wonder how well each of these chips does > on low-to-medium quality user code and current compilers.
As I see it, plenty of bandwidth and an excellent choice of cache sizes, latency and architecture. AMD had done a good job with Barcelona but didn't follow up with further improvements(other than cache size) with Shangai. Intel seems to have it the sweet spot. > > > It's a Core i7 but should give you an idea. >> > > I suspect that lots of people are holding their breaths (and POs) > waiting for Intel to release 2 (and 4?) socket nehalems. it has to be a > bit scary for AMD, since they're getting leapfrogged in the area > of their traditional strength. I don't have a sense for whether Goto's > kind of tuning (beyond the ability of compilers, and relatively > cache-friendly relative to flops) is terribly relevant to the market. It's even worse for AMD in some other areas. Take a look at this: http://it.anandtech.com/weblog/showpost.aspx?i=554 Best regards, Tiago Marques > > > on the topic of memory bandwidth: > http://techreport.com/articles.x/16448 > makes it sound as if AMD knows they have a scaling problem with cache > coherency, and have a solution queued. does anyone know whether nehalem > already has a probe filter? or if AMD has mentioned anything about > widening to a 3-4-dimm-per-socket memory interface? > > regards, mark hahn. >
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