Intel i86W Manual page 54

ADDRESSING
PAGE FRAME
I
DIR PAGE
I
OFFSET
I
I
PHYSICAL
ADDRESS
PAGE DIRECTORY
PAGE TABLE
~ PGTBLENTRY
1.......+
DIR ENTRY
-
I
DTB
I
I
240329i
Figure 4-4. Address Translation
The physical address of the current page directory is stored in the DTB field of the
dirbase
register. Memory management software has the option of using one page direc-
tory for all processes, one page directory for each process, or some combination of the
two.
4.2.4 Page-Table Entries
Page-table entries (PTEs) in either level of page tables have the same format. Figure 4-5
illustrates this format.
4.2.4.1 PAGE FRAME ADDRESS
The page frame address specifies the physical starting address of a page. Because pages
are located on 4K boundaries, the low-order 12 bits are always zero. In a page directory,
the page frame address is the address of a page table. In a second-level page table, the
page frame address is the address of the page frame that contains the desired memory
operand.
4-4