CPU to the north bridge (CPU bus), north bridge to memory (memory bus) at any time between the north and south bridge for data transmission, you need a channel, this channel is the north-south bridge bus. The wider the North-South bridge bus, the more convenient the data transmission. In the motherboard chipsets of each manufacturer, the north and south bridge buses have been given their own names. For example, Intel Hublink,VIA V-Link,Sis MuTIOL and other bandwidth bandwidth = clock frequency x bus bits \/8,