In some cases only some of the wires in a wire group are used as input and these are labeled as N lsb or N msb at the point where the wire group goes into the register. "lsb" stands for "least significant bits" meaning the lesser N bits of the wire group, as defined by the order of the flip-flops of the register from which they originate, and "msb" stands for "most significant bits," analogously.

Here are the exact wires that route into several components:

IR-OUT0 to IR-OUT11     go into port 0 of MARMUX
IR-OUT0 to IR-OUT11     go into port 1 of MBRMUX
PC-OUT0 to PC-OUT11     go into port 1 of MARMUX
S-OUT0 to S-OUT11       go into port 2 of MARMUX
IR-OUT8 to IR-OUT15     go into the instruction decoder