Вот цитата из одной умной книги, там про SQL речь ведется
Цитата:
A 32-bit machine can directly address only 4 GB of memory, and by default, Windows itself reserves the top 2 GB of address space for its own use, which leaves only 2 GB as the maximum size of the VAS for any application, such as SQL Server. You can increase this by enabling a /3GB flag in the system's Boot.ini file, which allows applications to have a VAS of up to 3 GB. If your system has more than 3GB of RAM, the only way a 32-bit machine can get to it is by enabling AWE. One benefit in SQL Server 2005 of using AWE, is that memory pages allocated through the AWE mechanism are considered locked pages and can never be swapped out.