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标题: 在Istanbul的帮助下，四路Opteron终于胜了双路Nehalem EP [打印本页]

作者: itany 时间: 2009-2-26 16:15
标题: 在Istanbul的帮助下，四路Opteron终于胜了双路Nehalem EP
How AMD's Istanbul might close the gap with Nehalem EP

Date: February 25th, 2009
Author: Johan De Gelas

The Istanbul cores are the same as those that can be found in the AMD's latest Shanghai CPU. But the "uncore" part of Istanbul is more interesting. By now, you have probably heard about AMD's "HT-assist" technology, a probe or snoop filter. Every time a new cacheline is brought into the L3-cache of for example CPU 1 on the current Shanghai Platform, a broadcast message is sent to all L3-caches of all CPUs, and CPU 1 has to wait until those CPUs answer.

In the case of Istanbul, the CPU will simply check it's snoop filter in it's own L3-cache, and if none of the other CPUs have that certain cacheline, it can go ahead. This lowers the latency of bringing in a new cacheline and raises the effective bandwidth.

To better understand this, we combined our own stream benchmarking with the one that AMD presented. All AMD systems are using DDR-2 800.

As each Stream thread works on its own data, there is no reason to send out coherency synchronization requests. These requests slow the process of getting new cachelines in the L3 and hence lower effective memory bandwidth. What is interesting is that this will not only benefit the applications that use the HT interconnects a lot for coherency traffic, but also applications like stream which do not need the HT interconnects. Also notice that HT 3.0 does not improve memory bandwidth, as Stream will try to keep its thread data local. Our testing used SUSE SLES 10 SP2 and AMD used Windows 2008. Both OSs are well optimized and NUMA aware.

This means that especially HPC applications, with many threads all working on their own data, will benefit from the higher effective bandwidth. Besides HT assist, AMD has now confirmed to us that the memory controller has been tuned quite a bit. This higher amount of bandwidth will allow the quad Istanbul to stay out of the reach of the dual Nehalem EP Xeons in many HPC applications.

HT assist might also improve the SAP and OLTP scores quite a bit, but for a different reason. SAP and OLTP applications perform a lot of cache coherency syncronization requests, so the snoop filter will substantially lower the average latency of such requests as in some cases:

the CPU will only wait on one other CPU (instead of waiting for all responses to come back)
the CPU won't have to wait at all, as the other CPUs don't have this line.

Secondly, this will also lower memory latency, which is a bonus for almost every multi-threaded application.

Lower memory latency, higher bandwidth, lower "cache coherency" latency and more interconnect bandwidth: the improved "uncore" of Istanbul will be vital to close the gap with Nehalem. Much will depend on how quickly Intel introduces its own hexacore 32 nm Xeons, but that probably won't happen before 2010. Istanbul is shaping up to be a really good alternative for Intel's quadcore Nehalem. We might see a good fight after all...

Don't forget to check it.anandtech.com (IT portal) often, as many of our blogposts (for example the VMworld 2009 coverage) are not published on the frontpage of Anandtech.com.

作者: Sirlion 时间: 2009-2-26 17:07
4路26核和2路8核？？？

作者: itany 时间: 2009-2-26 17:11

4路26核和2路8核？？？
Sirlion 发表于 2009-2-26 17:07

正是这个Stream Benchmark，AMD在发布会上对其津津乐道……
http://news.mydrivers.com/1/128/128324.htm

作者: Prescott 时间: 2009-2-26 17:31

AMD你也会有今天，哈哈哈哈。

作者: zaknafein 时间: 2009-2-26 18:45
正确的对法是4路24核24线程opteron完胜2路8核16线程nehalem ep

作者: Asuka 时间: 2009-2-26 19:26
{titter:] 2vs2的结果是显而易见的

{titter:] 期待8核心的喝奶

作者: the_god_of_pig 时间: 2009-2-26 19:35
A社不是喜欢玩"AMD xxxxx孤独求败"么，来呀{titter:]

作者: Sakray 时间: 2009-2-26 19:36
又见DDR2对DDR3。毫无意义的测试

作者: kojiboku 时间: 2009-2-26 19:52
AMD这代架构不行。。。
堆核心那么高成本再贱卖不是自杀啊？！
赶紧勒裤带换。。。

作者: YsMilan 时间: 2009-2-26 20:24
11# Sakray

你说没意义,可是AMD觉得很有意义啊

作者: Prescott 时间: 2009-2-26 20:52

{titter:] 2vs2的结果是显而易见的

{titter:] 期待8核心的喝奶
Asuka 发表于 2009-2-26 19:26

Nehalem-EX有四通道FBD2，2S平台Stream测试干掉Istanbul应该没啥问题。4S平台有望冲击100GB/s大关。

作者: Sakray 时间: 2009-2-26 21:14

11# Sakray

你说没意义,可是AMD觉得很有意义啊
YsMilan 发表于 2009-2-26 20:24

AMD觉得有意义关我啥事{closedeyes:] A就继续放烟雾弹吧

作者: NONO 时间: 2009-2-26 22:31
這樣還好意思拿出來比??{sweat:]

作者: elisha 时间: 2009-2-26 23:01
下面的评论都在指责anandtech饭A，哈哈哈哈

作者: hundrix 时间: 2009-11-1 18:04
搞得和HP PA-RISC vs IBM PowerPC一样，2个核才抵人家1颗
问之，答曰，每个核的价钱也是人家的一半嘛 -____-

作者: fordash 时间: 2009-11-1 22:53
看着挺有意思的。

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