7. North Bridge
The North Bridge connects to the faster buses, which are:
The processor bus, otherwise known as the system or front
side bus, connected to the CPU only, via a large square
socket.
The memory bus which connects to main memory. Usually
there are 2 - 4 long black slots with white clips at each end to
connect memory modules to this bus.
The AGP (Accelerated Graphics Port) bus. Developed from
the PCI bus described below, this is a high speed bus to
connect to one video adapter card only. The one AGP slot is
usually brown.
8. South Bridge
Linked to the North Bridge by a proprietary bus which we don't need to
consider, the South Bridge connects to the following slower buses, devices
and ports:
The PCI (Peripheral Component Interconnect) bus. This is used to connect
other adapter cards to the system. Motherboards usually have 3 - 6 white
slots, parallel to the AGP slot but slightly offset, which allow adapter cards to
connect to the PCI bus.
The IDE (Integrated Drive Electronics) or ATA (AT Attachment - does anyone
remember the IBM AT?) interface. Your hard disk and CR-ROM drives connect
to the South Bridge via broad flat "ribbon" cables plugged into two 40 pin
connectors on the motherboard.
The ISA (Industry Standard Architecture) bus. Being based on the original
IBM AT design, this has long slots usually black in colour adjacent to the PCI
slots. This older technology bus disappeared from most new
motherboards, although a few current Pentium III/Celeron motherboards still
have an ISA bus with one slot for compatibility with some older interface cards.
9. South bridge
USB (Universal Serial Bus) ports. These sit on the edge of the
motherboard so that they can be accessed from the rear of the
PC, together with all the other motherboard ports.
Super I/O chip which provides a floppy disk controller, two serial port
controllers and one parallel port controller. A single 34 pin connector
near the IDE connectors is used to connect to the floppy disk drive.
BIOS ROM (Basic Input Output System - Read Only Memory). The BIOS
is very low level software that interfaces between the operating system
and the hardware. It also includes the first software the CPU runs when
the system is turned on, which loads the operating system from the hard
disk into main memory and transfers control to it. For this reason, the BIOS
is stored in a ROM chip, which keeps its data intact even when power is
turned off.
