3-26 Vol. 3A
PROTECTED-MODE MEMORY MANAGEMENT
3.7.6 Page-Directory and Page-Table Entries

Figure 3-14 shows the format for the page-directory and page-table entries when 4-KByte

pages and 32-bit physical addresses are being used. Figure 3-15 shows the format for the

page-directory entries when 4-MByte pages and 32-bit physical addresses are being used. The

functions of the flags and fields in the entries in Figures 3-14 and 3-15 are as follows:

Page base address, bits 12 through 32

(Page-table entries for 4-KByte pages) — Specifies the physical address of the

first byte of a 4-KByte page. The bits in this field are interpreted as the 20 most-

significant bits of the physical address, which forces pages to be aligned on

4-KByte boundaries.

Figure 3-14. Format of Page-Directory and Page-Table Entries for 4-KByte Pages

and 32-Bit Physical Addresses

31
Available for system programmer’s use
Global page (Ignored)
Page size (0 indicates 4 KBytes)
Reserved (set to 0)
1211 9876543210
P
S
P
CA0
Accessed
Cache disabled
Write-through
User/Supervisor
Read/Write
Present
DP
P
W
T
U
/
S
R
/
W
GAvailPage-Table Base Address
31
Available for system programmer’s use
Global Page
Page Table Attribute Index
Dirty
1211 9 876543210
P
C
AD
Accessed
Cache Disabled
Write-Through
User/Supervisor
Read/Write
Present
DP
P
W
T
U
/
S
R
/
W
AvailPage Base Address
Page-Directory Entry (4-KByte Page Table)
Page-Table Entry (4-KByte Page)
P
A
T
G