In the second phase of address transformation, the 80386 transforms a linear address into a physical address. The page-translation step is optional. Page translation is in effect only when the PG bit of CR0 is set. This bit is typically set by the operating system during software initialization. Page Frame A page frame is a 4K-byte unit of contiguous addresses of physical memory.
Pages begin onbyte boundaries and are fixed in size.
Linear Address A linear address refers indirectly to a physical address by specifying a page table, a page within that table, and an offset within that page. Figure 5-8 shows the format of a linear address. Page Tables A page table is simply an array of 32-bit page specifiers. A page table is itself a page, and therefore contains 4 Kilobytes of memory or at most 1K 32-bit entries. Two levels of tables are used to address a page of memory.