Nintendo Ultra64 Programmer's Manual page 201

NOP
31 26 25
SPECIAL
0 0 0 0 0 0
6
Format:
nop
Description:
This instruction does nothing; it modifies no registers and changes no internal RSP state.
It is useful for program instruction padding or insertion into branch delay slots (when no useful
work can be done).
Operation:
T: nothing happens
Exceptions:
None
Revision 1.0
Null Operation
21 20 16 15
rs rt
5 5
11 10 6 5
rd 0
0 0 0 0 0
5 5
NOP
0
NOP
0 0 0 0 0 0
6
201