Confused about memory configuration and timings

[Lordberek]

I bought some Corsair XMS memory on Newegg for my new Nforce2 mobo and Barton CPU system.

Model was - CMX512-3200C2PT

There was another entry almost identical. It was listed with only two differences I could see... a platinum heat spreader, and the timings for the second were 64mx8 for the configuration vs. the 64mx64 that I bought.

What is the difference exactly and does it matter...