iPhone 5s: benefits of 64 bit processors if no more than 4 GB of RAM?

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http://superuser.com – My understanding is that the (main) reason of having a 64 bit processor, is to be able to use more than 4 GB of RAM. In PCs, it is now very common to have more than 4GB of ram, and to really be able to use such ram, you NEED a 64 bit processor. But for a smartphone, which (afaik) doesn't have more than 4GB of ram, what's the point? what is the benefit? What kind of apps benefit from it that will really make a difference ? Specific examples of apps taking advantage would be nice. Do final users will even notice a difference? Or is it just a marketing strategy? Note, i know a similar ques (HowTos)