Microsoft® Windows® 2000 Security Handbook

Memory

Windows NT's virtual memory system uses a flat, 32-bit address space, which gives you access to 4GB of memory. Most of the time, this space is split in halves: 2GB for the kernel and 2GB for user mode applications. I say most of the time because provisions have been in place since Windows NT Server 4.0 Service Pack 3 so that it is possible for servers to have access to more user space. Access to more than 2GB of address space is useful to hardcore server applications such as databases that manipulate huge data sets.

Figure 1.2 shows the logical layout of memory that processes see. Note that the logical layout is quite different from the physical layout. The Virtual Memory Manager maps the logical layout to the physical memory (and paging ...