How many amps does a 6 pin PCIe card uses

Here is my System configuration:

• Intel i7 950
• Geforce GTX 570
• Coolmax 800W PSU.
• ASUS P8Z77-V PRO motherboard
• Corsair 120GB SSD
• 1 TB HDD from Seagate
• G.skil 4GB RAM.

I would like to know power acquired by a 6 pin PCIe card. Because my Geforce GTX 570 has 6 pin connector and I have to attach PSU 6 pin connector to it. So it would be better if someone tell me about how much amps does a 6 pin PCIe card uses. In future I am going to add one more Geforce GTX 570 and configure both in SLI. So it would be necessary to know about the maximum capability of my PSU and the whole powered acquired from the side of GPU. The current power supply contains 2 PCIe power connectors (6 pin and a 6+2 pin.)

The PCIe power inputs or connectors are mainly used for the Graphics cards in order to supply addition power supply. Some Higher End card does need an external power supply from the PSU. The cards which may contain more than one fan over it usually opt for additional power. This the one reason, now all new range power supplies come with 2 extra connectors.

Here amount of voltage does not matter and how much power needs for the card. To connect, you should not use the molex to 6 pin adapter, you should only use 6 pin PCI Express power connector. The minimum requirement is power supply with +12 Volt current rating of 24 Amps

The Nvidia product page shows that the GTX 570 need almost 220W power. For a single card, you will at least need a 12V with 20A of current. So there card will not run from the 150W power which is supplies from the PCIe bus. The card can draw 20A of current from the two 6-pin connectors, it means it only draw 10A per 6-pin. You don’t need to worry about that.

In my case I am using the GTX 590 and It need almost 8-pin PCIe connector. The card has upgraded to 8 pins because of the increased current. On some handbook you will see that it draw 10 Amps but the manufacturer website shows that it takes 18 Amps. The fact is

• 6 pin PCIe connector (new) with three 12V wires, deliver 150W.
• 6 pin PCIe connector (old) with two 12 wires, deliver 75W.

So far I have learned several facts about the PCI-E connectors and its power output. I have researched a lot about it. Most of the PCI-E connecter has 6 pins but none of them used for power. In a 6 pin connector, the first and third pins are 12V and carry 8 Amps.pin. As per some graphics cards specification, the second pin is connected. However the fourth are sixth pins are Com return lines. The fifth pin is meant for sensing. So it clearly shows that a graphic card uses power only from the 2 lines and it get 12V*8A*2= 192Watts which is much somewhat below the requirement as I think.

On the other hand of there is a 8 pin PCI-E connector, 2 Com lines are added (4&8). The first, second and third contains 12V rail. Pin 5,7,8 are Com return lines and Pin 4 is a Com sensing. The remaining one is pin 6 and it is meant for pin connector sensing. So if total up 12V*8Amp*3=288 Watts, which is much above the requirement (i.e. 220w).

Other limitation means, the width of the PCB lines over the GPU which will only carry 1-2 Amps.

The 6Pin PCI-E connector is used to for extra 12 volt power needed by the graphic card or any other expansion card. Most graphics card like Geforce GTX 570 needs more than 75 watts provided supplied by the motherboard. These cards draw most power from the 12 volt rail. These are sometimes called as "PEG cables" where "PEG" stands for PCI Express Graphics.

GTX 570 is a very nice GPU and recommendation for that card is 550-watt PSU with a minimum of 38 amps on the +12 volt rail. It is provided in the specs. So you have 800W PSU and I don’t think that you have anything to worry about there. Also the GTX 570 has a lower TDP than GTX 580 (219 W versus 244 W). If you are going to use a mloex connector, then maximum current per molex pin is 11A, or 130w at 12v.

I would like to explain you briefly about the difference between the PCI-E 6-Pin to 8-Pin adapters. The actual wattage used by both PCI-E Connectors are:

• PCI-E 6-Pin = 75W
• PCI-E 8-Pin = 150W

However there is only one physical difference between PCI-E 6-Pin and PCI-E 8-Pin connection and it is two "ground" wires. There is no increment in amperage at all. So in theory, the PCI-E 6-Pin connections can only supply 150W with individual cable rated at 4.15A. Due to this people tend to use PCI-E 6-Pin to 8-Pin adapters instead of PCI-E 6-Pin cable. But one thing remembers that without having the proper knowledge about the amperage distribution and internal wiring, you should go for such adapters.