It's reported correctly, it really is lower. Resource contention FTL.
That graph is wrong.
The Core-i7 920 has four physical cores, eight virtual cores. The dots fit exactly what I see, making parallel computations on a Core-i7 2600K.
I use the programming language
Haskell for parallel programming on various machines. The language itself has a bit of a learning curve, but one can parallelize a program with a handful of extra lines of code. It is particularly sensitive to resource contention, known as the "last core slowdown." On a machine with eight physical cores, performance scales nicely up to seven cores, and craters if one uses all eight cores.
With four physical cores, eight virtual cores, one still gets worse performance using eight threads over seven. Performance scales nicely up to four threads, with a bit of a hill for 5, 6, or 7 threads.
In other words, virtual cores are a scheduling convenience, that allows one to use all four cores of a four core processor. It's a second order effect, even if a rather significant one.
So I believe the dots; I recognize their pattern. LinX looks like it's implemented in a less efficient language for parallel computations, but the appearance of the graph is qualitatively the same as I see with other problems.
I question the two lines. They don't apply to virtual cores.
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