Compaq 21264 - Manual (Page 164)

5–22 Internal Processor Registers Alpha 21264/EV67 Hardware Reference Manual
Ibox IPRs
Figure 5–24 Process Context Register
Table 5–14 describes 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] — —
63 39 9 38 8 47 46 5 4 13 3 12 2 1 0
ASN[7:0]
ASTRR[3:0]
ASTER[3:0]
FPE
PPCE
LK99-0032A