thats because DDR means that the speed is actually doubled.
ie PC2700 = 333DDR = 166mhz
PC 3200 = 400 DDR = 200 mhz
and so on.
Dual channel is only for when you have 2 identical ram modules,and you can slightly increase the performance by running them dual channel.
i think thats the problem your describing.
you can always download and install cpuz and check the ram and fsb speeds there.
good luck
Ripper
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