VR4102 datasheet(133/701 Pages) NEC

133 / 701 page

CHAPTER 5 MEMORY MANAGEMENT SYSTEM

133

(8) xkphys (64-bit Kernel mode, physical spaces)

When the KX = 1 in the Status register and bits 63 and 62 of the virtual address space are 10, the virtual

address space is called xkphys and selected as either cached or uncached. If any of bits 58 to 32 of the

address is 1, an attempt to access that address results in an address error.

Whether cache can be used or not is determined by bits 59 to 61 of the virtual address. Table 5-5 shows

cacheability corresponding to 8 address spaces.

Table 5-5. Cacheability and the xkphys Address Space

Bits 61-59

Cacheability

Start address

Cached

0x8000 0000 0000 0000

0x8000 0000 FFFF FFFF

Cached

0x8800 0000 0000 0000

0x8800 0000 FFFF FFFF

Uncached

0x9000 0000 0000 0000

0x9000 0000 FFFF FFFF

Cached

0x9800 0000 0000 0000

0x9800 0000 FFFF FFFF

Cached

0xA000 0000 0000 0000

0xA000 0000 FFFF FFFF

Cached

0xA800 0000 0000 0000

0xA800 0000 FFFF FFFF

Cached

0xB000 0000 0000 0000

0xB000 0000 FFFF FFFF

Cached

0xB800 0000 0000 0000

0xB800 0000 FFFF FFFF

(9) xkseg (64-bit Kernel mode, physical spaces)

When the KX = 1 in the Status register and bits 63 and 62 of the virtual address space are 11, the virtual

address space is called xkseg and selected as either of the following:

• kernel virtual space, xkseg, the current kernel virtual space; the virtual address is extended with the contents

of the 8-bit ASID field to form a unique virtual address

References to xkseg are mapped through TLB. Whether cache can be used or not is determined by bit C of

each page’s TLB entry.

• one of the four 32-bit kernel compatibility spaces, as described in the next section.

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