NEC Network Controller uPD98502 - Manual (Page 105)

CHAPTER 2 V R 4120A
Preliminary User’s Manual S15543EJ1V0UM 105
2.4.2.3 64-bit mode address translation
Figure 2-27 shows the virtual-to-physical-address translation of a 64-bit mode address. This figure illustrates the
two possible page size; a 1-Kbyte page (10 bits) and a 256-Kbyte page (18 bits).
— Shown at the top of Figure 2-27 is the virtual address space in which the page size is 1 Kbyte and the offset
is 10 bits. The 30 bits excluding the ASID field represents the virtual page number (VPN), enabling selecting
a page table of 1 G entry.
— Shown at the bottom of Figure 2-27 is the virtual address space in which the page size is 256 Kbytes and the
offset is 18 bits. The 22 bits excluding the ASID field represents the VPN, enabling selecting a page table of
4 M entries.
Figure 2-27. 64-bit Mode Virtual Address Translation
31
PFN
32-bit physical address
10 24 30 8
0
0 9 10 39 40 61 62 63 64 71
ASID
Offset
TLB
18 24 22 8
0 17 18 39 40 61 62 63 64 71
ASID
TLB
0 or -1
0 or -1 VPN Offset
VPN Offset
Bits 62 and 63 of the virtual
address select the user,
supervisor, or kernel
address space.
Virtual address for 4 M (2 22 ) 256-Kbyte pages
Virtual address for 1 G (2 30 ) 1-Kbyte pages
30 bits = 1 G pages
The offset is passed to
physical address without
being changed.
The offset is passed to
physical address without
being changed.
Virtual-to-physical address
translation with the TLB
Virtual-to-physical address
translation with the TLB
22 bits = 4 M pages