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[drfedja]

however, a single module would only be about 90% of the performance of two of Magny's cores.

JF doesn't said that. He said that the one module has 1.8x of performance scaling with two threads on it. Single module with two threads would be 90% of the performance of two BD modules with two threads. In other words CMT - clustered multithreaded module has 90% of chip multiprocessed two cores with same type of microarchitecture. There isn't comparison with Magny Cours or 10h.

Since I'm 98% sure what I read was by JF (John) anyways, this is just as valid as whatever blog post I'm referring to (though I think it might be one of the 20 Questions posts found here):
http://www.xtremesystems.org/forums/...1&postcount=67

He talks about mythical 6-core bulldozer:

Mythical 6-core bulldozer:
100% + 95% + 95% + 95% + 95% + 95% = 575%

Orochi die with 4 modules:
180% + 180% + 180% + 180% = 720%

What if we had just done a 4 core and added HT (keeping in the same die space):
100% + 95% +95% +95% + 18% + 18% + 18% + 18% = 457%

What about a 6 core with HT (has to assume more die space):
100% + 95% +95% +95% +95% +95% + 18% + 18% + 18% + 18% + 18% + 18% = 683%

And someone concluded that the IPC decreases. :d
And, from that moment, there is so much people who think that BD has decreased IPC from 10h.

beep: of course, but what is exactly IPC?

IPC = Instructions Per Cycle. This is a number who's tells us how many instructions CPU can retire per one cycle. Today modern Out Of Order processors have many execution units, they can execute more than one instruction per cycle, parallel, and out of order. Because program code is in order, there is quite difficult to make such machine to execute out of order, because of data dependencies, too many branches in code, etc.
IPC is software performance measuring unit. If code is properly optimised, it can run on CPU, or even GPU with more instructions per cycle. However, also if CPU is faster, than it can run same software with higher IPC number.

Maybe here is not talking about core to core, but about cores to cores (6 vs 8 etc)

If BD has 50% more throughput than 6-core 10h, at probably same clock, that means the server workload uses all cores. That means the core per core BD vs 10h, BD has 12.5% more throughput than 10h, but single module can do 25% more serialized, single thread jobs than one single core.