Each Silicon Graphics computer model has a particular set of device addresses. The choice of device addresses is part of the architecture of the whole computer system; it is not designed into the processor chip.
For example, the EISA bus attachment in the Indigo2(TM) responds to physical memory addresses beginning at 0x000A 0000. (The EISA bus is discussed in detail in Part VII, "EISA Drivers.") To see some actual device addresses, examine VECTOR statements in files in /var/sysgen/system.
In some cases, the relationship between device addresses and physical addresses can be changed dynamically. For example, in the Silicon Graphics Challenge and Onyx(TM) systems, different 8 MB portions of the VME bus address space can be mapped dynamically to different blocks of physical addresses. (VME bus details are in Part IV, "VME Device Drivers.")