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.[1] 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.
As shown in the picture below, it's common for the northbridge and southbridge to have a heat sink; in addition, the northbridge is usually slightly larger than the southbridge and is the closest to the CPU and memory.
