Explaining Chipsets, the Defining Piece of Your Motherboard - The South Bridge
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The south bridge does not connect directly to the CPU; it goes through the north bridge. It is also called the I/O Controller Hub (ICH), again, for reasons that will become obvious. It controls various I/O and onboard devices. These include:
• Hard disk drive ports (parallel and serial ATA ports)
• USB ports
• Onboard audio
• Onboard LAN
• PCI bus
• PCI Express lanes
• Real time clock (RTC)
• CMOS memory
• Legacy devices (i.e. floppy disk drive)
• BIOS
Whereas the north bridge affects your computer’s overall performance, the south bridge affects the features your system will have. Since it controls the number and speed of USB ports, it sets the number of peripherals your computer is capable of handling. Likewise, if you want a system that can handle multiple hard disk drives, you need to find out the capabilities of the south bridge in your chosen chipset.
As you might guess, since the south bridge does not communicate directly with the CPU, accessing certain pieces of information in your computer can take a little longer, depending on where they are located and what the system is trying to do at the same time. Accessing something located in RAM is relatively fast, since the CPU is connected directly to the north bridge, which communicates with RAM, and both of those connections are usually pretty fast. Accessing information located on the hard drive takes a little longer, however; the connection travels from the CPU through the north bridge to the south bridge. Remember the Intel 955x Express chipset, which features a connection between the GMCH and the CPU of 8 GB/sec? In that same chipset, the connection between the GMCH and the ICH is only 2 GB/sec.
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