You won't need more than 2 GB RAM for that.
Running XAMPP and a realmap with a 98 MB map takes 1,5 GB RAM.
Map size != Memory size. It's more factors to take into concern.
It varies from system to system - the way it's configured to handle large memory usage and caching, and so on.Fact is, that when you start a realmap it takes 3gb of your ram, after an hour it takes 2gb and after 4 - 5 hours its down to 1.5gb ram