do laptops have dual channel?
if it's positive why the one with two rams have the same bus as the the single ones? (I haven't tested but the sites say so,they have the same tec spec )
if they do,do all new platforms support it ?
Yes, laptops have dual channel.
I don't know if I've understood your question, but you can go on google and type dual-channel vs single, you'll see some tests that may help you. Dual channel increases performance, but doesn't do a big difference usually