Northbridge:
The Northbridge communicates with the fastest devices, namely the RAM and the video card.
Southbridge:
The Southbridge communicates with the slower devices such as the lower-throughput expansion buses, I/O parts, and integrated peripherals.
Communication with legacy devices, such as the floppy disk drive or the serial port, is usually delegated out to a circuit called the Super I/O chips.
In many recent system architectures, the CPU communicates with RAM directly, instead of relying on the Northbridge - and in the latest architectures, the Northbridge has been eliminated since the CPU possesses all of its functionality.
The ATX form factor - including full-sized, microATX, and FlexATX - dominates the PC market.
Motherboards support literally dozens of device types through integrated I/O and expansion slots.
Installation is a matter of placing standouts properly and screwing down the motherboard.
Troubleshooting is tough, though, because of all the variables in the computer, but the fix for a bad motherboard is simple : replace it.