▷ 24-pin atx and 8-pin eps power connectors what are they and what is it for?

A power supply unit (or PSU) converts AC power to a regulated, low-voltage DC power supply for the internal components of a PC. Modern personal PCs universally use switched mode power supplies. In this articles we are going to see the importance of the power supply and its most important connectors for the motherboard, the ATX and the EPS.

How a power supply works and its main connectors for the motherboard

The desktop computer's power supply changes AC power from a wall outlet to low-voltage DC power to operate the processor and peripheral devices. Various direct current voltages are required and must be regulated with some precision to provide stable operation of the computer.

First-generation microcomputers and power supply units for home computers used a heavy step-down transformer and linear power supply, as used, for example, the Commodore PET introduced in 1977. The Apple II, also introduced in 1977, it was noted for its switched mode power supply, which was lighter and smaller than an equivalent linear power supply, and had no cooling fan. The switched mode supply uses a high frequency transformer with a ferrite core and power transistors that switch thousands of times per second.

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All modern PCs now use switch mode power supplies, which are lighter, less expensive, and more efficient than equivalent linear power supplies. On the 200 to 350 W output PSUs, main transformers with a 19-28 input winding by 115V and 3 or 4 output windings by 6V were used. PC power supplies can have short circuit protection, overload protection, overvoltage protection, overvoltage protection, overload and over temperature protection.

The ATX standard followed the design of some manufacturers, so that the power supplies also supply a backup voltage, so that most of the computer system could be turned off after preparing for hibernation or shutdown, and turned back on by an event. When the PC is turned off, but the power supply is still on, it can be started remotely via Wake-on-LAN and Wake-on-ring or locally via Keyboard Power ON (KBPO) if the motherboard admits it. This reserve voltage is generated by a smaller power supply within the unit.

Most modern desktop PC power supplies comply with the ATX specification, which includes form factor and voltage tolerances. While an ATX power supply is connected to the mains, it always provides a standby voltage of 5 volts (5VSB) for standby functions and certain peripherals to be turned on. ATX power supplies are turned on and off by a signal from the motherboard. They also provide a signal to the motherboard to indicate when the DC voltages are in the specifications, so that the computer can safely start and start.

24-pin ATX and 8-pin EPS connectors, differences and importance

The 24-pin ATX cable or main connector on the motherboard is one of the cables that you need to connect to your PC's motherboard. This cable uses a large 24-pin connector, which is the largest connector found on the power supply. Most power supplies will allow you to convert this 24-pin connector into a 20-pin connector, generally by removing the additional 4 pins, which is the standard used by older motherboards.

Motherboards that use the 24-pin connector are called ATX12V 2.x, while motherboards that use the 20-pin connector can be ATX12V 1.x or an ATX motherboard. Please note that these names refer to the electrical connection of the motherboard and not the physical size of the motherboard. ATX is also a name that is used to describe the size of the motherboard, which can be confusing for some users, you may have an ATX motherboard with an ATX12V 2.x connector. For example, in this case, ATX refers to the size of the motherboard, 12 "x 9.6" or 30.5 cm x 24.4 cm.

As for the EPS12V connector, it is an 8-pin connector that has the same function as the previous one, that is, to provide electrical power to the system CPU. Since it has eight pins instead of four, it is capable of providing more current. Not all power supplies and all motherboards come with this connector. On some power supplies, the EPS12V connector is obtained by joining two ATX12V connectors. If your motherboard and power supply have this connector, use it instead of using the ATX12V.

The motherboards that come with this connector often come with half of the connector covered with a sticker or a plastic cover, allowing the ATX12V connector on the power supply to be used on the EPS12V connector on the motherboard. You can install the ATX12V connector on the power supply to the EPS12V connector on the motherboard, however this is not recommended.

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Differences between 24-pin and 20-pin ATX connector

The original ATX standard supported a 20-pin connector with a pinout very similar to the current 24-pin connector, but with the 11, 12, 23, and 24 pins omitted. The 20-pin connector belongs to the oldest ATX standard, while the 24-pin connector follows the latest ATX standard. The 24-pin connector is just the 20-pin cable with 4 additional cables to provide additional electrical power. As long as your power supply can provide enough power to the motherboard, you can still use a 20-pin power supply.

This means that the newer 24-pin power supply is useful for motherboards that require more power and therefore eliminates the need for ATX 12V power supplies to provide an auxiliary power cable, although some may still do what. The additional four pins are generally removable, allowing it to be used in a 20-pin motherboard connection. The additional pin block just hangs over the connector on the motherboard, they don't connect to anything. Some motherboards allow the opposite: use the older 20-pin power cable on a 24-pin motherboard connection. If you need to use a non-detachable 24-pin power connector on a motherboard that only accepts a 20-pin cable, there are a number of online stores where you can buy a 24-pin to 20-pin adapter.

AT power supplies, already out of service

The first IBM PC AT power supply unit supplied two main voltages: +5 V and +12 V. It supplied two other voltages, −5 V and −12 V, but with limited amounts of power. Most of the microchips of the time worked with 5 V of power. Of the 63.5 W that these PSUs could deliver, most of it was on this +5 V rail. The + 12V source was primarily used to operate motors such as disk drives and cooling fans. As more peripherals were added, more power was supplied to the 12V rail.

However, since most of the power was consumed by the chips, the 5V rail still delivered most of the power. The −12 V rail was primarily used to provide negative supply voltage to the RS-232 serial ports. A −5 V rail was provided for peripherals on the ISA bus (such as sound cards), but was not used by the motherboard. An additional cable called 'Power Good' was used to prevent the digital circuit from operating during the initial milliseconds of power supply turn-on, where the output voltages and currents increase but are not yet sufficient or stable, for the correct operation of the device. Once the output power is ready to use, the correct power signal indicates to the digital circuits that it can begin to operate.

Original IBM AT PC power supplies included a line voltage power switch, which extended through the side of the PC case. In a common variant found in tower boxes, the line voltage switch was connected to the power supply with a short cable, allowing it to be mounted separately from the power supply.

An early power supply was fully on or off, controlled by the line-voltage mechanical switch, and low power consumption idle modes were not a design consideration for early power supplies. These power supplies generally were not capable of energy saving modes. Due to the always-on design, in the event of a short circuit, a fuse would blow, or a switched mode supply would cut off the power repeatedly, wait a short time, and try to restart. For some power supplies, the repeated reset is audible as a quick, quiet chirp emitted from the device.

So far our article on 24-pin power connectors and EPS What are they and what is it for? We hope you liked it and will help you better understand the importance of your PC's power supply.

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