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An addressing mode specifies how an instruction obtains an operand or forms an effective memory address. Examples include immediate operands, processor register operands, base-plus-displacement memory access and scaled processor register indexing.

A useful additional mode is base plus scaled register indexing, with effective address $B+(I\ll s)$. For an array of four-byte elements choose $s=2$, use its base address on the unshifted ALU input and its index processor register on the barrel shifter input, then add. This forms an indexed machine word address in one datapath pass. An eight-byte element uses $s=3$.

With parallel ALU and barrel shifter outputs, shifting and adding require either separate instructions/cycles or another route from the barrel shifter to the ALU. The new serial connection supplies that route. This is an addressing mode capability, not a claim that the old instruction encoding already contains the new mode.