The websites are not always up to date on their information. I just checked and your model is not specifically listed on the Crucial website.
Until NOW (like in last month or two) the best you could get was Dual Channel memory, and dual channel motherboards. All performance systems used dual channel and the memory would be used in matching pairs. All memory was not always dual channel. Times change and technology moves forward.
The new Intel i7 CPUs are the FIRST EVER TRI Channel memory, and for performance the memory is installed in THREE matching chips. For that matter this is the first time ever that Intel put the memory controller on the CPU itself instead of the Northbridge chip (AMD has done this for a couple of years).
Do you really truly believe that the Dell rep has a clue of how this stuff works; seriously?
Check out this article to understand a little bit more about how your new CPU works. i7 CPU
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