As Figure 14.16 shows, the set of mapped addresses do not need to be identical in
both address spaces. The goal is to make a bridge transparent so the processor does not
know about the auxiliary bus. From a programmer’s point of view, however, the
software may need to accommodate the mapping. For example, when a device is installed
in an auxiliary bus, the device is configured with an address, A. If the
computer’s owner enters A as the device address, software must understand the mapping
and use the corresponding address on the main bus. Similarly, if the interaction
between the device and the processor involves addresses, the processor must use addresses
that the auxiliary device understands