Hardware Reference
In-Depth Information
Figure 1.15
Architecture of a modern PC supporting several bus standards
(AGP, PCI
,
and ISA).
Bridge handles all of the system I/O, including an interface to the IDE/ATA bus
(see page 53).
Figure 1.17 shows the typical layout of a modern PC motherboard. This sys-
tem employs an architecture which is based on a bus controller (North Bridge)
and an I/O controller (South Bridge), and an AMD Socket 7 processor. Four
ISA and three PCI expansion slots are provided. By contrast, an example of an
embedded PC controller is shown in Figure 1.18. This system is based on an
AMD processor (designed specifically for embedded controller applications)
and uses the PC/104 expansion architecture (see Chapter 2).
PC memory
The PC system board's read/write memory provides storage for the memory
resident parts of the operating system (e.g. Windows, Linux, or DOS) as well
as user applications programs and transient data. Read/write memory is also
used to store data that is displayed on the screen. On some systems this mem-
ory is separate from the system board's read/write memory (and usually fitted
to a specialized graphics card) whilst on others it is 'mapped' into the main
