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A–8 Alpha Instruction Set
21264/EV68A 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