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and practices 289 ch08.indd 289 12/14/09 2:49:14 PM All-In-One / CompTIA Network+ All-in-One Exam Guide / Meyers & Jernigan / 170133-8 / Chapter 8 CompTIA A+Certification All-in-One Exam Guide 290 Historical/Conceptual
Structure and Function of the Expansion Bus
As you’ve learned, every device in the computer—whether soldered to the motherboard
or snapped into a socket—connects to the external data bus and the address bus. The
expansion slots are no exception. They connect to the rest of the PC through the chipset. Exactly where on the chipset varies depending on the system. On some systems, the
expansion slots connect to the Southbridge (Figure 8-1). On other systems, the expansion slots connect to the Northbridge (Figure 8-2). Finally, many systems have more
than one type of expansion bus, with slots of one type connecting to the Northbridge
and slots of another type connecting to the Southbridge (Figure 8-3).
Southbridge Figure 8-2
Northbridge The chipset provides an extension of the address bus and data bus to the expansion
slots, and thus to any expansion cards in those slots. If you plug a hard drive controller
card into an expansion slot, it functions just as if it were built into the motherboard, albeit with one big difference: speed. As you’ll recall from Chapter 5, “Microprocessors,” ch08.indd 290 12/14/09 2:49:15 PM All-In-One / CompTIA Network+ All-in-One Exam Guide / Meyers & Jernigan / 170133-8 / Chapter 8
All-In-One Chapter 8: Expansion Bus 291 Figure 8-3
and Southbridge the system crystal—the clock—pushes the CPU. The system crystal provides a critical
function for the entire PC, acting like a drill sergeant calling a cadence, setting the pace
of activity in the computer. Every device soldered to the motherboard is designed to run
at the speed of the system crystal. A 133-MHz motherboard, for example, has at least
a 133-MHz Northbridge chip and a 133-MHz South...
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This note was uploaded on 04/27/2010 for the course COMPTIA 1201 taught by Professor N/a during the Spring '10 term at Galveston College.
- Spring '10