32位操作系統-內存管理之32位分頁模式 實現

A logical processor uses 32-bit paging if CR0.PG = 1 and CR4.PAE = 0. 32-bit paging translates 32-bit linear 
addresses to 40-bit physical addresses.1 Although 40 bits corresponds to 1 TByte, linear addresses are limited to 
32 bits; at most 4 GBytes of linear-address space may be accessed at any given time. -來自IA32文檔