System Buses - HP 400 Series Servicing Manual

Virtual and physical addresses are references to data storage locations, based on the
total size of the data storage area. A virtual address is the operating system's way of
referring to a memory location, based on the size of memory from the object's point
of view (virtually unlimited). A physical address is an absolute physical location in the
system's total memory space. The location can be on the system's memory boards (the
main memory) or in a memory component on any other board in the system.
3.1.2

System Buses

Figure 3-1 through Figure 3-5 show the functional organization of the buses and the
bus interfaces on the CPU boards of the different Series 400 system models. The DIO
system bus provides the main channel for address and data flow among the following
system components:
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Microprocessor
Floating-Point Coprocessor
Memory Control and Memory
ISA bus Programmable I/O (PIO) interface
Graphics interface
HP-IB interface
Utility Interface
Small Computer Systems Interface (SCSI)
Theory of Operation 3-3