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標題: [硬件] Know why Conroe/Meron is so fast with some synthetic benchmarks? [打印本頁]

作者: Richteralan 時間: 2006-4-20 07:42 標題: Know why Conroe/Meron is so fast with some synthetic benchmarks?

作者: HEAVEN‧傑 時間: 2006-4-20 09:18

no

作者: Totti 時間: 2006-4-20 09:56

CHEAT

作者: Richteralan 時間: 2006-4-20 09:59

Because those synthetic benchmarks\' work load can fit into Conroe/Meron\'s 4MB L2 cache.
Thus it can run extremely fast.

Once the work load is larger than 4MB, Conroe is slower than Athlon 64 clock by clock.

作者: Richteralan 時間: 2006-4-20 10:06

Just some quick test to let you guys know that synthetic benchmarks can be manipulated:

引用:

AMD Opteron(tm) Processor 144
CPU speed: 2646.28 MHz
CPU features: RDTSC, CMOV, Prefetch, 3DNow!, MMX, SSE, SSE2
L1 cache size: 64 KB
L2 cache size: 1024 KB
L1 cache line size: 64 bytes
L2 cache line size: 64 bytes
L1 TLBS: 32
L2 TLBS: 512
Prime95 32-bit version 24.14, RdtscTiming=1
Best time for 512K FFT length: 17.604 ms.
Best time for 640K FFT length: 23.012 ms.
Best time for 768K FFT length: 27.951 ms.
Best time for 896K FFT length: 33.391 ms.
Best time for 1024K FFT length: 37.258 ms.
Best time for 1280K FFT length: 47.333 ms.
Best time for 1536K FFT length: 58.072 ms.
Best time for 1792K FFT length: 70.158 ms.
Best time for 2048K FFT length: 78.418 ms.
Best time for 2560K FFT length: 102.758 ms.
Best time for 3072K FFT length: 125.455 ms.

Above is a run of prime95 on my Opteron 144 Venus core.
It has a 1MB L2 cache.
By analysing the best time, you can see from 512K to 640K, the increased time is only 6ms. From 640K to 768K only 5ms, etc.

But when you compare 1024K and 1280K, you\'ll see the time increased for 10ms. From 1280K to 1536K, a 11ms margin, etc.

So, guess what?

作者: HEAVEN‧傑 時間: 2006-4-20 10:09

引用:

Originally posted by Richteralan at 2006-4-20 09:59:
Because those synthetic benchmarks\' work load can fit into Conroe/Meron\'s 4MB L2 cache.
Thus it can run extremely fast.

Once the work load is larger than 4MB, Conroe is slower than Athlon 64 cl ...

真巧合

作者: Richteralan 時間: 2006-4-20 10:10

引用:

Originally posted by HEAVEN‧傑 at 2006-4-20 10:09:

真巧合

唔明?

作者: HEAVEN‧傑 時間: 2006-4-20 10:18

引用:

Originally posted by Richteralan at 2006-4-20 10:10:

唔明?

又會咁岩得咁橋fit哂既

作者: Richteralan 時間: 2006-4-20 10:24

引用:

Originally posted by HEAVEN‧傑 at 2006-4-20 10:18:

又會咁岩得咁橋fit哂既

唔一定要fit曬.
Any work load smaller than 4MB

作者: HEAVEN‧傑 時間: 2006-4-20 10:40

引用:

Originally posted by Richteralan at 2006-4-20 10:24:

唔一定要fit曬.
Any work load smaller than 4MB

靠L2

作者: Richteralan 時間: 2006-4-20 10:50

引用:

Originally posted by HEAVEN‧傑 at 2006-4-20 10:40:

靠L2

synthetic benchmark就可以咁玩姐.....
現實中既軟件邊可以咁玩

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