Compaq EV68A 14describes the process context register fields, 22Internal Processor Registers

Ibox IPRs

Figure 5–24 Process Context Register

63 47 46 39 38 13 12 9 8 5 4 3 2 1 0

ASN[7:0]
ASTRR[3:0]
ASTER[3:0]
FPE
PPCE
					LK99-0032A
	Table 5–14describes the process context register fields.
Table 5–14 Process Context Register Fields Description
Name	Extent	Type	Description
Reserved	[63:47]	—	—
ASN[7:0]	[46:39]	RW	Address space number.
Reserved	[38:13]	—	—
ASTRR[3:0]	[12:9]	RW	AST request register—used to request AST interrupts in
			each of the four processor modes.
			To generate a particular AST interrupt, its corresponding
			bits in ASTRR and ASTER must be set, along with the
			ASTE bit in IER.
			Further, the value of the current mode bits in the PS register
			must be equal to or higher than the value of the mode associ-
			ated with the AST request.
			The bit order with this field is:
			User Mode	12
			Supervisor Mode	11
			Executive Mode	10
			Kernel Mode	9
ASTER[3:0]	[8:5]	RW	AST enable register—used to individually enable each of
			the four AST interrupt requests.
			The bit order with this field is:
			User Mode	8
			Supervisor Mode	7
			Executive Mode	6
			Kernel Mode	5
Reserved	[4:3]	—	—

5–22Internal Processor Registers 21264/EV68A Hardware Reference Manual