PCB News - Interpreting the wiring design of the motherboard 　

1. The concept of equal length of clock line

On a motherboard, the distance from the North Bridge chip to the CPU, memory, and AGP slots should be equal. This is the basic requirement of motherboard design, the so-called "clock line equal length" concept. As the bridge between the CPU and the memory, the Northbridge chip is very particular about the layout. For example, some motherboard manufacturers with development capabilities adopt a clever design that rotates 45 degrees in the layout of the north bridge chip, which not only shortens the wiring length between the north bridge chip and the CPU, memory socket and AGP socket, but also more The clock lines can be made the same length.

2. Misunderstanding of snake walking line

Snake line is a common form of wiring on computer motherboards (people who have played the Nokia mobile game "Snake" should not be unfamiliar). The wiring design on the motherboard is a professional knowledge. Some people think that the more snaking lines, the higher the design level. This view is wrong.

In fact, there are two reasons for adopting a snake line on a motherboard:

One is to ensure the equal length of the wiring lines. Because the clock line from the CPU to the Northbridge chip is different from the circuit board circuit of ordinary household appliances, the signals running at high speed at a frequency of about 100MHz on these circuits are very sensitive to the length of the PCB circuit. Clock lines of unequal length will cause the signal to be out of sync, and then cause system instability. Therefore, certain lines must be routed in a curved manner to adjust the length.

Another common reason for using a snake line is to minimize the impact of electromagnetic radiation (EMI) on the rest of the motherboard and the human body. Because of the high speed and monotonous digital signal, it will interfere with the normal operation of various parts in the motherboard. Usually, an easy way for motherboard manufacturers to suppress EMI is to design a serpentine line to absorb as much radiation as possible. However, we should also see that although the use of serpentine lines has the above benefits, it does not mean that the more serpentine lines used when designing the motherboard wiring, the better. Because too many and dense motherboard traces will cause uneven layout of the motherboard, which will have a certain impact on the quality of the motherboard. Good wiring should make the line density of each part of the motherboard have little difference, and should be distributed as evenly as possible, otherwise it is easy to cause the instability of the motherboard.

The above is the introduction of interpreting the wiring design of the motherboard. Ipcb is also provided to PCB manufacturers and PCB manufacturing technology.