Do you need to use both the 6 pin PCI-E power cable and the 8 pin PCI-E power cable on a video card? Why are they used? To give power to the video card if needed? Seems like the motherboard gives the card power as well?
Different cards have different power requirements. Yes, you need to connect all of the power cables. For example the Radeon 5770 has only a single 6-pin connector and runs fine on a 450W power supply, while the Radeon 4870 and GTX 250 require two power connectors from 500-550W (or higher) psu. Cards draw some power directly from the slot (They can draw more under PCI-E 2.0 and later than version 1.1 or 1.0)
if the graphics card has an 6-pin power connector and an 8-pin connector then u need to use the 6-pin and the 8-pin power cable from your power supply.most power supplies (especially those that supply 500 watts of power to your cpu and all the peripherals) in the market right now have at least one connector for each type (6-pin and 8-pin).usually the most high-end power supplies now (like the Ultra X4 series) have more than 1 for each type.right now the most high-end power supplies from my perspective is the 1600W power supply from the Ultra X4 series.it has 3 6-pin power connectors and 3 for the 8-pin power connector. and ya the 6- and 8-pin power connector is the bridge for the power supply to transport power to the component. nope.the motherboard is a selfish guy.it doesnt give power to the graphics card unless the graphics card doesn't take a lot of wattage to work then the motherboard will donate power to the graphics card.
