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[Sandra 2005 SR3]CPU數量與Memory Bandwidth 疑惑

各位前輩,弟發現一個Sandra奇怪的問題。
話說前幾天閒閒無事,小弟就來測測公司的Server好了,手上剛好有Sandra 2005 SR3,
那就來測測CPU跟Memory的笑能好了....
本來一切都在預料的結果,但是沒想到在測Memory Bandwidth這項的時候,
發現一個怪怪的問題,原本26xx MB/s的Int分數,在我手癢拔掉一顆CPU後竟然飆到
31xx MB/s...
後來發現:
DualCPU+DualCore SingleCPU+DualCore SingleCPU+SingleCore
.......26xx......................31xx............................33xx.......

有大大遇過這樣的狀況嗎??? 還是本來就是這樣,只是弟耍笨而已???

P.S 不要說沒圖沒真相,因為弟不是MIS,所以其他的資訊可能要趁晚上摸黑去抓了..

先請各位大大解惑啦....
     
      
舊 2006-02-10, 02:49 PM #1
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617離線中  
BorgMu
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加入日期: May 2002
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沒硬體列表沒真相
 
舊 2006-02-10, 03:27 PM #2
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BorgMu離線中  
617
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我先用我小小的頭腦,把硬體給撞出來好了...
M/B: Intel SE7520??
CPU: Xeon 3.6x2
RAM: Infineon 1Gx2,Dual Channel.
其他的真的要晚上去看看了....
有大大有idea嗎?? 因為我用Google神查了一下午,也查不出來甚麼,請大家給展明燈吧..
舊 2006-02-10, 05:10 PM #3
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雜碎
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同樣的一筒水分成兩管還是集中一管那一個水壓的比較大
舊 2006-02-10, 06:29 PM #4
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617
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雜大,小弟資質差,可否明示一些....
我猜想大大的意思是Sandra只會測一個CPU對Memory的流量,所以當雙CPU時因為平均使用的關係,所以benchmark變低了嗎???應該自行加倍嗎??
但是我以為result下面的Total test threads是說同時會執行得數目,Sandra會自行x倍數的???我誤解了嗎??還請多多指教....感謝感謝...^^
舊 2006-02-10, 09:35 PM #5
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617
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查到的,看樣子是小弟自己會錯意了,難怪沒有人要回...Orz...

Q: Why don't I get higher scores with HyperThreading/SMT enabled?
A: SMT does NOT help in memory transfers. The bandwidth available to each CPU is the same, thus using all cores would increase overhead resulting in lower scores. We're looking into using SMT for prefetching into future versions of the benchmark.

Q: I get lower scores in my HyperThreaded/SMT system than with a non-SMT CPU!
A: Please update to Sandra 2002 (8.59) or later for full SMT support. Earlier versions have data alignment issues.

Q: If the benchmark is multi-threaded, why don't I get higher indexes on a SMP system?
A: The benchmark is OK. You can verify by looking at the load, number of threads and memory utilisation in Task Manager of Windows NT/2000/XP.

The issue is the bus that connects the CPUs. If it is shared and not point-to-point (e.g. Intel's (A)GTL+ as used in PPro/PII/PIII/4) the CPUs are sharing the same bandwidth so you won't see much increase due to the huge amount of data transferred by the benchmark. Since the benchmark is memory limited (in order to be correct), one CPU or more won't make much difference since the memory bus is the bottleneck. When the bus is not much utilised you get close to N increase in performance (where N is no of CPUs), otherwise you get no/small performance gain.

Q: In my SMP system all memory benchmarks (ALU, FPU, MMX, SSE2 etc.) return the same score! Why is that?
A: See above. This shows that the benchmark is working, i.e. the limit of memory throughput is reached - when no matter what you use to load/store it does not make any difference.
舊 2006-02-13, 02:30 PM #6
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