Been away a while, but I think the matter is automatic recognition. That is, even though the 3000 is at 133, the processor is correctly recognised when Ratio is set to Auto.
As said above, level 1 cache is a major thing. That is for example one of the reasons Athlons work so much better than Pentiums at equal MHz.
I'd advice against setting to 166 on this mobo, as that is a major overclock.
And Grayone is of course more thorough on this and other points.