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A–8
Alpha Instruction Set
Alpha 21264/EV67 Hardware Reference Manual
Reserved Opcodes
A.2 Reserved Opcodes
This section describes the opcodes that are reserved in the Alpha architecture. They can
be reserved for Compaq or for PALcode.
A.2.1 Opcodes Reserved for Compaq
Table A–3 lists opcodes reserved for Compaq.
STW
Mem
0D
Store word
SUBF F-P
15.081
Subtract
F_floating
SUBG
F-P
15.0A1 Subtract G_floating
SUBL Opr
10.09
Subtract
longword
SUBL/V
Opr
10.49
Subtract longword with integer overflow enable
SUBQ Opr
10.29
Subtract
quadword
SUBQ/V
Opr
10.69
Subtract quadword with integer overflow enable
SUBS
F-P
16.081 Subtract
S_floating
SUBT
F-P
16.0A1 Subtract T_floating
TRAPB
Mfc
18.0000 Trap barrier
UMULH
Opr
13.30
Unsigned multiply quadword high
UNPKBL
Opr
1C.35
Unpack bytes to longwords
UNPKBW
Opr
1C.34
Unpack bytes to words
WH64
Mfc
18.F800 Write hint — 64 bytes
WMB
Mfc
18.4400 Write memory barrier
XOR Opr
11.40
Logical
difference
ZAP
Opr
12.30
Zero bytes
ZAPNOT
Opr
12.31
Zero bytes not
Table A–3 Opcodes Reserved for Compaq
Mnemonic
Opcode
Mnemonic
Opcode
OPC01
01
OPC05
05
OPC02
02
OPC06
06
OPC03
03
OPC07
07
OPC04
04
—
—
Table A–2 Architecture Instructions (Continued)
Mnemonic
Format
Opcode
Description
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