A northbridge or host bridge is one of the two chips in the core logic chipset architecture on a PC motherboard, the other being the southbridge. Unlike the southbridge, northbridge is connected directly to the CPU via the front-side bus (FSB) and is thus responsible for tasks that require the highest performance. The northbridge is usually paired with a southbridge, also known as I/O controller hub.
In systems where they are included, these two chips manage communications between the CPU and other parts of the motherboard, and constitute the core logic chipset of the PC motherboard.
On older Intel based PCs, the northbridge was also named external memory controller hub (MCH) or graphics and memory controller hub (GMCH) if equipped with integrated graphics. Increasingly these functions became integrated into the CPU chip itself,beginning with memory and graphics controllers. For Intel Sandy Bridge and AMD Accelerated Processing Unit processors introduced in 2011, all of the functions of the northbridge reside on the CPU,while AMD FX CPUs still require external northbridge and southbridge chips.
在旧的intel主机上面，北桥也被叫做外部 memory controller hub (MCH) 内存控制总线或者 graphics and memory controller hub (GMCH)图形与内存控制总线如果配备了集成显卡。渐渐地这些功能开始随着内存和图像控制器集成到cpu芯片里面。对于Intel Sandy Bridge和在2011年推出的AMD Accelerated Processing Unit处理器，所有的北桥的功能都在cpu里面。但是AMD FX CPUs系列任然需要外部的南桥和北桥芯片组。
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 systems with Intel chipsets, the southbridge is named I/O Controller Hub (ICH), while AMD has named its southbridge Fusion Controller Hub (FCH) since the introduction of its Fusion APUs.
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.