In its day, components with chips such as the processor or graphics card, or even logic circuits, used a voltage of 5V to operate, while other components such as fans, sound cards or other elements required 12V. Over the years, the clock speed of these chips has been increasing and with it so has the consumption, and yet for example the CPU voltage has dropped to 3.3V. This means that the power supply had to be able to provide different voltages To be able to meet the needs of the components precisely, which is why the three different voltages that a modern power supply uses emerged: 3.3V, 5V and 12V.
12V lines in power supplies
To define what these voltage lines are in power supplies, the best way to do it is with a simile: imagine that, simply, the power supply is a converter that first transforms the alternating current that comes from the plug to direct current, since it is what the PC needs to work, and then it transforms the voltage that comes from the electrical outlet to the voltages that the PC needs to work: 12V, 5V and 3.3V. In the past, negative voltages of -5V and -12V were also necessary, but in modern power supplies they have already disappeared because they have long since ceased to be necessary.
As the internal structure of a processor became smaller and smaller and at the same time operating speeds increased, the core voltage dropped and ended up becoming variable. On the other hand, motherboards or graphics cards used their own integrated voltage regulators that drew only the power they needed from the 12V lines of the power supply.
This means that over the years, 12V lines or rails became the most important power supply lines for all voltages a PC uses and indeed even power supplies that carry DC technology. / DC create their own 5V and 3.3V internally from the 12V line, which is why these rails are often referred to as “minor” and 12V rails “major”.
Do multi-lane fountains have an advantage?
In the field of 12V lines in power supplies we can find models that have a single rail capable of providing a huge amperage, or models with several lanes that deliver lower amperage. Multi-lane sources have an exclusive OCP (Over Current Protection) for each of them, which is used to regulate the maximum current in each lane; This is a very useful function since, in addition to having greater protection against short circuits and overloads in the connected devices, it allows a finer regulation on the voltage.
On the contrary, the sources that have a design with a single 12V line do not have OCP protection per lane but only the generic one of the source in general, thus increasing the risk that cables and components have problems; in return, it delivers full power and a more uniform workload across the lane, which is especially important for use with power-hungry graphics cards or if the processor is overclocked, for example.
Therefore, having a single 12V line or several has its advantages and disadvantages; You will always hear that for high-performance systems it is better to use a single and powerful 12V rail and it really is, but if your PC does not consume as much or if your source is oversized, then you should use a source with several rails for greater security.
How can you check the voltage of the 12V rail?
Although power supplies have multiple filters and regulators to provide the most stable voltage possible, they do not always get too fine a setting as this is highly dependent on the load on the system. The best way, or at least the most reliable way to check what values are being delivered, is by accessing the PC BIOS and in the section “Hardware monitoring”, “PC Health Status” or similar (since it depends on the motherboard) you will see the voltages the motherboard is receiving from the power supply.
The 12V voltage reading should always be between 11.8V and 12.4V, and should be stable with little or no fluctuation. A slight fluctuation of 0.05V is generally fine as long as it doesn’t happen more than once every 10-15 seconds; a larger fluctuation of 0.1V can be safe as long as it does not occur more than once every minute, while a fluctuation of more than 0.1V every 10 seconds or less could be an indication that the source is in trouble on the 12V lines (note that while in the BIOS, the PC is completely idle and there should be no fluctuation).
If you want to take these readings with the PC running and / or under load, you will have to resort to monitoring software such as Aida64, a software that is capable of delivering fairly reliable readings. It is common, in this case, that the fluctuations are much greater and especially if you are subjecting the PC to a benchmark or testing it in a game; In this case, as long as the rail remains between the safe values you should not worry.