AMD cores can complete proccesses in less clock cycles than Intel cores, therefore they are clocked lower.
To put it into perspective to you, imagine an AMD proccesor being a large tire and an Intel proccessor being a small tire. The larger tire can move a farther distance in one rotation than the smaller tire, so the smaller tire has to compensate by making more rotations to keep up.
Imagine the rotations being the clock speed, an AMD uses a lower clock speed because it completes proccesses faster, but Intel must use a faster clock speed to complete the same proccess at the same speed.
It's a bit complicated, but that's the best I can explain it.
Intel C2D E6320 / AMD Athlon X2 3800+
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2GB OCZ Gold PC2-6400 / 2GB OCZ Gold PC4000
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2x500GB / 320GB
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