VR4102 datasheet(119/701 Pages) NEC

119 / 701 page

CHAPTER 5 MEMORY MANAGEMENT SYSTEM

119

5.2.2 32-bit Mode Address Translation

Figure 5-2 shows the virtual-to-physical-address translation of a 32-bit mode address. The pages can have five

different sizes between 1 Kbyte (10 bits) and 256 Kbytes (18 bits), each being 4 times as large as the preceding one

in ascending order, that is 1 K, 4 K, 16 K, 64 K, and 256 K.

— Shown at the top of Figure 5-2 is the virtual address space in which the page size is 1 Kbyte and the offset is

10 bits. The 22 bits excluding the ASID field represents the virtual page number (VPN), enabling selecting a

page table of 4 M entries.

— Shown at the bottom of Figure 5-2 is the virtual address space in which the page size is 256 Kbytes and the

offset is 18 bits. The 14 bits excluding the ASID field represents the VPN, enabling selecting a page table of

16 K entries.

Figure 5-2. 32-bit Mode Virtual Address Translation

Bits 31 to 29 of the virtual

address select the user,

supervisor, or kernel

address space.

PFN

Virtual address for 16K (2

14) 256-Kbyte pages

Virtual address for 4M (2

22) 1-Kbyte pages

22 bits = 4M 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

ASID

Offset

VPN

Offset

TLB

14 bits = 16K pages

ASID

VPN

Offset

TLB

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