i was sure that overclocking is linear with the speed [heard that pcsx2 very cpu dependant]
but i thought dual core means a little more.. [some said that almost x2... maybe that 19% is because of your gpu limitations? it can be checked with AA/BF]
And AA, BF slow down only if your [and my too

] graphic card is not strong enought compared to the CPU.
I think we should make test from the same save point, where there are no optional polygons.. [random walking peoples

]
so we could compare our resoults..
When i will be home i will try to make a little test in my P4C.