virtual memory --> PTE/page table entry --> memory/paging (RAM/disk)
PTE : is the map table
In windows 32bit: 2GB is for kernel space, the other 2GB for shared/user.
32bit means it can allocate only up to 4GB memory.
The division means that each user process can have up to 2GB of virtual memory address.
/3GB ==> makes each user process can have up to 3GB (3072MB)
/USERVA ==> is a way to offset the lack of memory for PTE (PTE is in kernel space??).
So if /3gb is used, and /userva is used (ex. =3030), the PTE can have additional space as much as the substraction of them (3072-3030MB=42MB additional for kernel space : free PTE).
More detail : http://support.microsoft.com/kb/810371
/PAE ==> is a way to have more than 4GB memory recognised by the OS. It does not mean each process can have more than 2GB (or 3GB with /3GB on), but it means that there are some more space in memory to be used instead to be paged out to disk.
Wanna know deeper about address in memory, go to :
http://www.cs.cornell.edu/~tomf/notes/cps104/virtual.html
http://everything2.com/title/Page+Table+Entry
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