South Bridge is a chipset that is used for controlling I/O
Functions such as USB, disk interfaces, PCI Bus, Super I/O Chip support etc. In
other words it works as peripheral controller. The main feature of Southbridge
is that same South Bridge can be used with different types of North bridges. It
is generally located at the lower edge of the motherboard.
Following are some Major Functions Performed by South
Bridge:
I/O Control: South Bridge is the key point that
decides which kinds of buses, at what speed, and which features will be
supported by the system. South bridge controls PCI and ISA buses and transfers
information to them or from them.
USB Ports Control: USB Support on the motherboard is
provided by the south bridge and which is the main interface for mostly
peripheral devices.
Bus Bridge Support: Two main type of buses ISA and
PCI are used in most of the modern computers. Since, there is a great speed
mismatch between them. South Bridge provides the feature of connecting these
two dissimilar buses. This is achieved by PCI-to-ISA bridge chip.
Functions as Interrupt Controller: Interrupt is a
CPU request generated by either a Hardware or Software. Interrupt controller is
used to decide which request will be serviced first, how will be serviced and
how other requests will be handled. For
this purpose generally PIC 8259 is used. South Bridge incorporates all the
features of PIC Intel 8259 and reduces manufacturing cost and extra space
requirements on the motherboard.
Functions as DMA Controller: DMA is the function
of chipset that provides a way to transfer data between I/O device and memory
without the involvement f CPU. This functionality is not supported by most of
the peripherals and is replaced with a new technique called Bus Mastering. Bus
Mastering is a technique in which device not only transmits data to memory
directly but actually takes control of buses and performs transfers itself
without using DMA controller. This Bus Mastering feature is also Provided by
the South Bridge.
ATA/IDE Interface Support: South Bridge provides
two IDE interfaces where four HDD can be connected, two HDDs at each interface
in Master slave mode. These drives are on PCI bus and save an expansion slot,
which also reduces the cost.
Power Management: Another important feature of
South Bridge is Power Management to reduce amount of power used by PC during
idle periods.
Plug n Play Device Support: This feature allows
Automatic detection of new devices to Operating System and BIOS. Detected
devices are than assigned appropriate resources such as IRQ,I/O Port Addresses
and DMA Channels.
Audio Sound Interface: Interfacing support of
Audio device such as High Definition sound devices is also provided by the
South Bridge.
Ethernet Support: South Bridge also provides
support for interfacing Ethernet ports on the motherboard and its control.
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