Maybe I should explain it a little differently. All devices may have some sort of CPU. What I mean by CPU vs. ASIC. ASIC based devices (i.e. switches) mean that the Chip deals with the port and not the "software".
Perfect example is 4500s and 6500s. During the ROMMON mode you cannot set the TFTP to communicate with your PC on port G3/47... The only ports available are the ones on the Sup Module. It goes the same with any router that the only one available is e0/0. Now as for a switch, since all ports are handled by a separate set of chipsets usually a set of 4 or 8 ports are handled by one chip. These chips are non functional in ROMMON. IOS has to loaded and small firmwares get loaded on them to communicate with the IOS. The only way to push a bin file to flash on a switch without a Mgmt port is thru Console's XModem.