The different meanings of different power cord colors

The power supply is the heart of the host computer, providing energy for the stable operation of the computer. The number of output wires of power supplies positioned in different market segments may vary, but they are inseparable from the colorful 9 colors: yellow, red, orange, purple, blue, white, gray, green, and black (currently mainstream power supplies have omitted white wires). So, what do these different colors represent? What is the corresponding relationship between them and voltage?

Yellow: +12V

The yellow lines should be the most numerous in the power supply. With the addition of CPU and PCI-E graphics card power supply components, the role of +12V in the power supply is crucial.

+12V provides power for the spindle motor and seek motor of the hard disk, optical drive, and floppy drive in the PC, and provides working voltage for the ISA slot and the logic signal level of circuits such as serial port devices. When the +12V voltage output is abnormal, it often causes unstable disk reading performance of the hard disk, optical drive, and floppy drive. When the voltage is low, the optical drive will have serious disk picking, the hard disk's logical bad sectors will increase, bad sectors will often appear, the system will easily freeze, and it will not be able to be used normally. When it is high, the speed of the optical drive is too high, it is easy to lose control, and it is more likely to explode the disk. The hard disk will stall and spin fast. At present, if the +12V power supply is short, it will directly affect the performance of the PCI-E graphics card and the CPU, directly causing a freeze.

Red: +5V

The number of +5V wires is equal to that of yellow wires. +5V power is the working voltage provided to CPU and integrated circuits such as PCI, AGP, ISA, etc. It is the main working power supply in the computer. At present, CPUs use a mixed power supply of +12V and +5V, and the requirements for it are not as high as before. It is just that the latest Intel ATX 12V 2.2 version has strengthened the power supply capacity of +5V and strengthened the power supply of dual-core CPU. The quality of its power supply is directly related to the system stability of the computer.

Orange: +3.3V

This is a special setting for the ATX power supply to provide power for the memory. The latest 24pin main interface power supply focuses on strengthening the +3.3V power supply. This voltage has strict requirements, stable output, small ripple coefficient, large output current, and must be more than 20 amps. For safety reasons, some mid-to-high-end motherboards use high-power field tubes to control the power supply of the memory, but this tube may be burned out if the memory is inserted incorrectly. For platforms that use +2.5V DDR memory and +1.8V DDR2 memory, the motherboard is equipped with a voltage conversion circuit.

Purple: +5VSB (+5V standby power)

The ATX power supply provides +5V 720MA power to the motherboard through PIN9, which provides power for WOL (Wake-up On Lan), boot circuit, USB interface and other circuits. If you do not use network wake-up and other functions, please turn off such functions and remove the jumper to prevent these devices from drawing current from the +5VSB power supply. The power supply quality of this output directly affects the power consumption of the computer when it is in standby mode, which is directly linked to our electricity bill.

Blue: -12V

The -12V voltage provides the logic judgment level for the serial port, which requires a small current, generally below 1A. Even if the voltage deviation is too large, it will not cause failure, because the logic level 0 level has a wide range from -3V to -15V.

White: -5V

Currently, there are very few power supplies on the market with white wires. The white -5V also provides judgment levels for logic circuits. It requires very small current and generally does not affect the normal operation of the system. It is basically dispensable.

Green: P-ON (power switch terminal)

The power supply is turned on by the level. When the signal level of this port is greater than 1.8V, the main power supply is off; if the signal level is lower than 1.8V, the main power supply is on. Use a multimeter to test the output signal level of this pin, which is generally around 4V. Because the voltage output by this pin is the signal level. Here is a preliminary method to judge whether the power supply is good or bad: use a metal wire to short-circuit the green port and any black port. If the power supply does not respond, it means that the power supply is damaged. Many power supplies now have protection circuits. After short-circuiting the power supply, it will automatically shut down if there is no additional load. Therefore, everyone needs to carefully observe the power supply startup for a moment.

Gray: P-OK (power signal line)

Generally speaking, if the output of the gray line P-OK is above 2V, then the power supply can be used normally; if the output of P-OK is below 1V, the power supply will not guarantee the normal operation of the system and must be replaced. This is also one of the main means to judge the life of the power supply and whether it is qualified.

Knowing the corresponding relationship between the power supply output wire and the voltage can help us understand the output specifications of the power supply more clearly, which is very useful when purchasing a power supply and troubleshooting power supply failures.