SouthBridge

A typical southbridge/northbridge layout

The southbridge is one of the two chips in the core logic chipset on a personal computer (PC) motherboard, the other being the northbridge. The southbridge typically implements the slower capabilities of the motherboard in a northbridge/southbridge chipset computer architecture. In Intel chipset systems, the southbridge is named Input/Output Controller Hub (ICH). AMD, beginning with its Fusion APUs, has given the label FCH, or Fusion Controller Hub, to its southbridge.

The southbridge can usually be distinguished from the northbridge by not being directly connected to the CPU. Rather, the northbridge ties the southbridge to the CPU. Through the use of controller integrated channel circuitry, the northbridge can directly link signals from the I/O units to the CPU for data control and access.

Due to the push for System-on-a-chip (SoC) processors, modern devices increasingly have the northbridge integrated into the CPU die itself; examples are Intel's Sandy Bridge and AMD's Fusion processors (both released in 2011). In such cases the southbridge is being directly connected to the CPU. Intel's Haswell, expected to be available in 2013, is expected to feature the southbridge on the same package as the CPU for the Ultrabook platform.

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NorthBridge

Northbridge

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The northbridge has historically been one of the two chips in the core logic chipset on a PC motherboard, the other being the southbridge. Increasingly these functions have migrated to the CPU chip itself, beginning with memory and graphics controllers. For Intel Sandy Bridge and AMD Fusion processors introduced in 2011, all of the functions of the northbridge reside on the CPU. When a separate northbridge is employed in older Intel systems it is named memory controller hub (MCH) or integrated memory controller hub (IMCH) if equipped with an integrated VGA.

NorthBridge

Separating the different functions into the CPU, northbridge, and southbridge chips is due to the difficulty of integrating all components onto a single chip. In some instances the northbridge and southbridge functions were combined onto one die when design complexity and fabrication processes permitted it, for example the Nvidia GeForce 320M in the 2009/2010 Macbook Air is a northbridge/southbridge/GPU combo chip.

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Mother board

The motherboard is the main component inside the case. It is a large rectangular board with integrated circuitry that connects the other parts of the computer including the CPU, the RAM, the disk drives (CD, DVD, hard disk, or any others) as well as any peripherals connected via the ports or the expansion slots.
Components directly attached to the motherboard include:

• The central processing unit (CPU) performs most of the calculations which enable a computer to function, and is sometimes referred to as the "brain" of the computer. It is usually cooled by a heat sink and fan. Newer CPUs include an on-die Graphics Processing Unit (GPU).
• The chip set mediates communication between the CPU and the other components of the system, including main memory.
• RAM (random-access memory) stores resident part of the current running OS (OS core and so on) and all running processes (application parts, using CPU or input/output (I/O) channels or waiting for CPU or I/O channels).
• The BIOS includes boot firmware and power management. The Basic Input Output System tasks are handled by operating system drivers. Newer motherboards use Unified Extensible Firmware Interface instead of BIOS.
• Internal buses connect the CPU to various internal components and to expansion cards for graphics and sound.

• Current
• The north bridge memory controller, for RAM and PCI Express
• PCI Express, for expansion cards such as graphics, lannd and physics processors, and high-end network interfaces
• PCI, for other expansion cards
• SATA, for disk drives
• ATA
• Obsolete
• AGP (superseded by PCI Express)
• VLB VESA Local Bus (superseded by AGP)
• ISA (expansion card slot format obsolete in PCs, but still used in industrial computers)
• External bus controllers support ports for external peripherals. These ports may be controlled directly by the south bridge I/O controller or based on expansion cards attached to the motherboard through the PCI bus.
• USB
• FireWire
• SATA
• SCSI

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