Egy bizonyos szint felett a RAM nem segit, mivel az alkalmazasok jelentos resze nem memoria- vagy CPU-korlatos, hanem I/O-korlatos. Az I/O cache merete is csak veges, nem minden file lehet memory-mapped. Peldaul ha van egy 4-6 gigas terkepi adatbazisod, azt nem tudod normalisan szerkeszteni 8G RAM mellett sem.
A CreateFileMapping 2G-nal kevesebbet tud mappelni a memoriaba.
http://msdn.microsoft.com/en-us/library/aa366542%28VS.85%29.aspx
"The size of a file mapping object that is backed by a named file is limited by disk space. The size of a file view is limited to the largest available contiguous block of unreserved virtual memory. This is at most 2 GB minus the virtual memory already reserved by the process."