Specifications
Intel
®
64 and IA-32 Architectures Software Developer’s Manual Documentation Changes 215
Documentation Changes
Because a PDPTE is identified using bits 47:30 of the linear address, it controls access to
a 1-GByte region of the linear-address space. Use of the PDPTE depends on its PS flag
(bit 7):
1
...
• If the PDPTE’s PS flag is 1, the PDPTE maps a 1-GByte page (see Table 4-14). The
final physical address is computed as follows:
1. The PS flag of a PDPTE is reserved and must be 0 (if the P flag is 1) if 1-GByte pages are not sup-
ported. See Section 4.1.4 for how to determine whether 1-GByte pages are supported.
Table 4-14 Format of an IA-32e Page-Directory-Pointer-Table Entry (PDPTE) that Maps
a 1-GByte Page
Bit
Position(s)
Contents
0 (P) Present; must be 1 to map a 1-GByte page
1 (R/W) Read/write; if 0, writes may not be allowed to the 1-GByte page referenced by this
entry (depends on CPL and CR0.WP; see Section 4.6)
2 (U/S) User/supervisor; if 0, accesses with CPL=3 are not allowed to the 1-GByte page
referenced by this entry (see Section 4.6)
3 (PWT) Page-level write-through; indirectly determines the memory type used to access
the 1-GByte page referenced by this entry (see Section 4.9)
4 (PCD) Page-level cache disable; indirectly determines the memory type used to access
the 1-GByte page referenced by this entry (see Section 4.9)
5 (A) Accessed; indicates whether software has accessed the 1-GByte page referenced
by this entry (see Section 4.8)
6 (D) Dirty; indicates whether software has written to the 1-GByte page referenced by
this entry (see Section 4.8)
7 (PS) Page size; must be 1 (otherwise, this entry references a page directory; see
TableTable 4-15.)
8 (G) Global; if CR4.PGE = 1, determines whether the translation is global (see Section
4.10); ignored otherwise
11:9 Ignored
12 (PAT) Indirectly determines the memory type used to access the 1-GByte page
referenced by this entry (see Section 4.9)
1
29:13 Reserved (must be 0)
(M–1):30 Physical address of the 1-GByte page referenced by this entry
51:M Reserved (must be 0)
62:52 Ignored