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Asher
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Calgary, Alberta
Nov 1999 time: 22:29
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05-07-2003 20:55
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#11
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Re: Re: Re: Massive speed increase attained with compiler optimisations for Opteron
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Support Apolyton
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Also, the compiler speed improvements they talk about are against the Portland Group's old compiler, not the Intel C++ compiler that AMD uses to submit results.
quote: Originally posted by Urban Ranger
Because Opterons will unseat P4 Xeons. |
Where did it say that? 
Again, this is a bit misleading.
According to the author, the AMD system had 1GB of DDR333, the P4 1.7GHz had 256MB of PC800 RDRAM, and the 2.53GHz had 512MB of DDR266. And they have the 533MHz system bus and no HyperThreading.
The author also says the reason why the Opteron is fast in this benchmark is the code fits in the Opteron's 1MB L2 cache but not in the P4's 512KB, coupled with the slow memory and outdated system bus on the P4 it doesn't look so well.
It also doesn't mention how these machines are clustered, for all we know the P4s were connected with 10Mbps LAN and Opterons 1000Mbps... 
Not to mention just how plain fishy the numbers are, a 1.7GHz P4 beat a 2.53GHz P4... 
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Wraith
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Austin, Texas, USA
Aug 1999 time: 23:29
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Because the P3 doesn't take nearly the same hit from a branch mispredict, as you know very well. The small L1 cache isn't helping, either.
You should also note that they said their code doesn't use more than 32 MB of memory, so the size of RAM is pretty much irrelevant for these benchmarks, although the type won't be.
The Opterons are running in 32 bit mode on those, btw. They didn't have any 64 bit OSes installed.
Please, Asher, you understand this stuff. Take off your Wintel blinders for a bit and think about the code and the architectures. This is a very specific type of scientific code. Yes, there are some things the P3s will do better than the P4s. There are some areas the P4s will kick butt in, and there are some where they're going to be completely spanked by the Opterons. That's just how it works when you have different design goals.
Wraith
A=B and B=C therefore A=C {except where void or prohibited by law}
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Lord Merciless
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Why UR loves Opteron above Itanium is beyond me. After all, Opteron is supposd to be more backward compatible, more compatible to the very 32 bit version of Windows UR hates so much.
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