Compaq EV68A specifications Virtual Address Format Register Vaform, VAFORM32, Bendian

Ebox IPRs

Table 5–3describes the virtual address control register fields.

Table 5–3 Virtual Address Control Register Fields Description

Name	Extent	Type	Description
VPTB[63:30]	[63:30]	WO	Virtual Page Table Base.
			See the VA_FORM register section for details.
Reserved	[29:3]	—	—
VA_FORM_32	[2]	WO	This bit is used to control address formatting when reading the
			VA_FORM register. See the section on the VA_FORM register for
			details.
VA_48	[1]	WO,0	This bit controls the format applied to effective virtual addresses
			by the VA_FORM register and the memory pipe virtual address
			sign extension checkers. When VA_48 is clear, the 43-bit virtual
			address format is used, and when VA_48 is set, the 48-bit virtual
			address format is used.
			When VA_48 is set, the sign extension checkers generate an
			access control violation (ACV) if VA[63:0] ≠ SEXT (VA[47:0]).
			When VA_48 is clear, the sign extension checkers generate an
			ACV if VA[63:0] ≠ SEXT(VA[42:0]).
B_ENDIAN	[0]	WO	Big Endian Mode.
			When set, the shift amount (Rbv[2:0]) is inverted for EXTxx,
			INSxx, and MSKxx instructions. The lower bits of the physical
			address for Dstream accesses are inverted based upon the length
			of the reference as follows:

Byte:	Invert bits [2:0]
Word:	Invert bits [2:1]
Longword:	Inverts bit [2]

5.1.5 Virtual Address Format Register – VA_FORM

The virtual address format register (VA_FORM) is a read-only register. It contains the virtual page table entry address derived from the faulting virtual address stored in the VA register. It also contains the virtual page table base and associated control bits stored in the VA_CTL register.

Figure 5–5shows VA_FORM when VA_CTL(VA_48) equals 0 and

VA_CTL(VA_FORM_32) equals 0.

Figure 5–5 Virtual Address Format Register (VA_48 = 0, VA_FORM_32 = 0)

63 33 32 3 2 0

VPTB[63:33]

VA[42:13]

LK99-0011A

Figure 5–6shows VA_FORM when VA_CTL(VA_48) equals 1 and VA_CTL(VA_FORM_32) equals 0.

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