If you look at today’s power table you will see that, as a general rule, they will have these three voltages (some are still repairing) -12V and 5Vsb rail, but they have already used it in very modern systems. In addition, each rail, in addition to expressing its power in volts, corresponding to the current strength they can provide, measured in amperes.
Why does the electrical power of a PC operate at different voltage?
The first PC, made by IBM, offers only two different power types: + 12V and + 5V (also provided -12V and -5V but with limited power values). Most microchips at that time were operating at 5V, but in some parts with motors such as heavy drivers and fans, a high voltage was required, so a + 12V rail was installed. In addition, as the demand for craftsmen grew, the + 12V power line became more important because they were the ones they were using.
For its part, the VV railway used to be located at the port of RS-232, and the 5V railway was accessible from the ISA bus, like sound cards, but was never used by anyone other than that. that’s why he disappeared.
Later, when Intel developed the ATX standard for power in 1995, microchips started using low voltage so it was necessary to use the + 3.3V rail. Thus, starting in 1995, the famous 80486DX4 power lines began to have three main modern power lines: 12, 5 and 3.3 volts.
The ATX connector in the power supply provides all the required voltages directly to the motherboard for its many cables and power connections. Another addition to the ATX standard was the addition of a + 5Vsb (side) train to provide a small amount of “set” power even with the PC turned off, but as we discussed earlier with PC state power supply this is no longer necessary. to this day many sources no longer exist.
What power supply does each PC component use?
After what you have already described, you will know that electrical power has many different properties due to the electrical needs of each PC computer, so now is the time to see which component uses each voltages, and especially why everything is not integrated so everything works in the same amount of power.
- + 12V: processor, graphics card, fans and other PCIe expansion cards. And the main voltage of the motherboard, though it has to go through its VRM to control. Generally, it is a train that serves hardware components for very high usage.
- + 5V: hard drives, optical drives, other PCIe and USB expansion cards. All USB ports on a PC operate at 5V, and that includes the actual one you connect to.
- + 3.3V: RAM and SSD memory in M.2 format. In addition, all PCIe bases are capable of providing + 3.3V.
The reason is that the sources have different amounts of electricity and as a result the different railways are because of the electrical needs of the elements. As the transistors became smaller and smaller on the chips, it became better for them to operate with smaller amounts of electrical power, and this became even more important as the density of the processors increased.
Offering large amounts of low-power power to the processor, since Pentium era motherboards start installing a gas regulator so they can control for themselves what voltage and power are given to each component. Most modern processors may need to reach 100A in 2V or less, so it is not advisable to take these values on a + 12V train and be able to do it in a low-volume one, as it adds less work to the controller.