The bit pattern in $8
is moved to $9
($8
is unchanged).
or $9,$8,$0 # $9 <— contents of $8.
Copying the pattern in a source register to a destination register is called a move operation, even though the source register does not change. It really should be called "copy" but is not.
or d,s,$0 # $d gets copy of bit pattern in $s.
(Review:) How can a particular bit pattern be loaded into a register?