Compaq EV68A specifications Virtual Address Register VA, Virtual Address Control Register Vactl

Ebox IPRs

Table 5–2describes the CC_CTL register fields.

Table 5–2 Cycle Counter Control Register Fields Description

Name	Extent	Type	Description
Reserved	[63:33]	—	—
CC_ENA	[32]	WO	Counter Enable.
			When set, this bit allows the cycle counter to increment.
COUNTER[31:4]	[31:4]	WO	CC[31:4] may be written by way of this field. Write transactions
			to CC_CTL result in CC[3:0] being cleared.
Reserved	[3:0]	—	—

5.1.3 Virtual Address Register – VA

The virtual address register (VA) is a read-only register. When a DTB miss or fault occurs, the associated effective virtual address is written into the VA register. VA is not written when a LD_VPTE gets a DTB miss or Dstream fault. Figure 5–3shows the vir- tual address register.

Figure 5–3 Virtual Address Register

63 0

VA[63:0]

LK99-0010A

5.1.4 Virtual Address Control Register – VA_CTL

The virtual address control register (VA_CTL) is a write-only register that controls the way in which the faulting virtual address stored in the VA register is formatted when it is read by way of the VA_FORM register. It also contains control bits that affect the behavior of the memory pipe virtual address sign extension checkers and the behavior of the Ebox extract, insert, and mask instructions. Figure 5–4shows the virtual address control register.

Figure 5–4 Virtual Address Control Register

63 30 29 3 2 1 0

VPTB[63:30]

VA_FORM_32

VA_48

B_ENDIAN

LK99-0014A

5–4 Internal Processor Registers 21264/EV68A Hardware Reference Manual