The Power Connectors

Beginning with the NV7 (NVIDIA nForce) series of motherboards, ABIT began making all their Socket-A motherboards ATX12V-capable via the addition of the four-pin +12V power connector. This +12V power connector is normally found only in Intel Pentium 4 motherboards. According to Intel's ATX Power Supply Design Guide, the ATX main power connector is only capable of handling about 6A of power per contact. As such, ATX12V power supplies are only intended for applications where the motherboard demand for current exceeds the ATX main power connector's capability.

ATX12V-capable
- the ATX main power connector with the +12V power connector

You may wonder why, since other manufacturers do not seem to be following the trend. We asked ABIT about this and here's their reply :-

The standard ATX power connector is defined as below :-

+12V  --> 1 wire
+5V    --> 4 wires
+3.3V --> 3 wires

In NVIDIA's reference design, the CPU Vcore is converted from the +12V power line. Let's see what happens when the CPU consumes a lot of power. We will use the AMD Athlon XP 2800+ as an example. Because it has a maximum thermal output of 74.3W, the power supply will have to supply it 6.2A of current via that single +12V wire! That's quite hot and dangerous! Here's how we arrived at that figure :-

Current = ( Watt / Voltage)
            = ( CPU Vcore x CPU current ) / 12V
            = (1.65V x 45A ) / 12V
            = 6.2A

So, we designed the ATX12V connector for the NVIDIA nForce2 and VIA KT400 boards. With two +12V wires from ATX12V connector, the CPU will get the power from three, rather than just one +12V wire. That's a lot cooler and safer. It also allows the board to support newer processors with higher power consumption.

Well, that certainly makes a lot of sense, doesn't it? While most power supplies should be able to supply at least 15A of current on the +12V wire, the single +12V wire in the ATX main connector is only capable of supporting 6A of current! As such, it has reached its limit with the AMD Athlon XP 2800+ processor. Future processors will need more power and the ATX main connector will be hard-pressed to handle the load.

ABIT's solution of adding the extra four-pin +12V connector allows them to divide the load down three +12V wires. This will greatly reduce the load on each wire and the amount of heat produced. It will also allow the board to support processors with greater power requirements down the line. Kudos to them!

With that said, you can still use the board without using the +12V power connector. This allows the board to be used with both ATX and ATX12V power supplies.

Positioning Of The Power Connectors

The placement of the power connectors near the I/O panel is not particularly ideal. It forces the ATX power cable to cross over the CPU cooler to get to them. This can impede the air flow to the fan and reduce the cooler's performance. However, with judicious bending of the power cables, it's possible to mould them so that there will be a significant gap between the power cables and the fan. This prevents the cables from obstructing the fan inlet.

  
Crossing over the CPU cooler.

In the first picture above, it appears that the cables are blocking part of the fan inlet. But if you view it from the side (second picture), you will see that there's sufficient gap for the fan to operate at maximum performance. So, while the placement of the power connectors necessitate the crossing over of the cables, it's an easily correctable problem. Better this than the power connectors blocking the installation of large coolers when placed to the right of the CPU socket!