Nintendo Ultra64 Programmer's Manual page 176

JR
31
SPECIAL
0 0 0 0 0 0
Format:
jr rs
Description:
The program unconditionally jumps to the address contained in general register
one instruction.
Since instructions must be word-aligned, a Jump Register instruction must specify a target register
rs
( ) whose two low-order bits are zero.
Since the RSP program counter is only 12 bits, only 12 bits of the calculated address are used.
Operation:
T:
T+1:
Exceptions:
None
176
26 25 21 20
rs
6 5
temp  GPR[rs]
temp
PC
11...0
Jump Register
0
0 0 0 0 0 0 0 0 0 0 0 0 0 0 0
15
11...0
JR
6 5 0
JR
0 0 1 0 0 0
6
rs , with a delay of