yes
With the non-extended assembler there is
an addu d,s,t
instruction where
d, s, and t are registers
There is also
and an
addiu d,s,imm instruction where
imm is an immediate operand.
With the extended assembler the
addu d,s,x
instruction translates into different basic instructions
depending on x.
x can be a register, a 16-bit immediate operand, or a
32-bit immediate operand.
Examine the following instruction (for the extended assembler):
addu $t0,$s0,40000
The decimal value 40000 is too large to represent in 16 bits,
(the range for 16 bits is -32768 to +32767)
so the instruction cannot be translated into a basic
addiu
instruction.
Two instructions must be used to add $s0 to 4000010
and to place the result in $t0.