Connecting a GPU to a PSU

[Wano97]

To avoid breaking my GPU, I thought I'd ask it first. So in the past I've always had my GPU (2 x 8pin) connected to 2 x 6 pins on my PSU (PSU came with 8 pin to 6 pin cables), which worked fine (though it would sometimes crash under very heavy load). I just noticed it also has 2 x 6+2 pin connections on the PSU. Can I connect those to the 2 x 8 pin GPU?

[kelvinhall05]

Yeah, if they're meant for the GPU, why not?

[FloRolf]

Wait what exactly have you done in the past? Which motherboard has 2x6pin power out? 

 

Edit: ah, you edited. Ofc always fill ALL the pins on your GPU. 

[Fasauceome]

6 pin PCIe delivers 75 watts. 6+2 pin PCIe delivers double that.

 

Definitely use the 6+2 connectors. Never use an adapter for 6 to 8 pin.

[Wano97]

4 minutes ago, FloRolf said:

Wait what have exactly have you done in the past? Which motherboard has 2x6pin power out? 

my PSU has a 2x 6pin power out (and 2x 8 pin)

[mariushm]

13 minutes ago, Fasauceome said:

6 pin PCIe delivers 75 watts. 6+2 pin PCIe delivers double that.

 

Definitely use the 6+2 connectors. Never use an adapter for 6 to 8 pin.

NO.  The cables don't know anything, they'll transfer as much energy as the video card demands.

 

If you have issues that you think are caused by the power quality, it's more likely that the power supply can not provide that amount of energy, and changing the cables won't make a difference.

 

The PCI-E Standard says that a video card should not take more than 75w from a 6pin connector, or 150w from a 8 pin connector - the wires and the physical connectors are capable of much more than that, the 6pin connector for example is good for up to around 3 pairs of wires x 9A per pair x 12v = 324 watts.

The 9A is a physical limitation of the metal pins inside the housing (the plastic of the connectors) - more is possible but you risk overheating the connectors or having loose connections inside the connectors. There are also connectors rated for more (ex 12-13A per contact), especially for EPS (cpu 8 pin), which use thicker filled pins capable of carrying safely more current.

 

So because a video card can not be called pci-e video card and can't put on the box any mention of pci-e if they exceed this amount of power drawn from the power supply, that's what happens... the video card bios will refuse to work with a 6 pin cable inside instead of 8 pin, even though it could. 

The two extra pins in the 8pin connector are just used to give the video card the "permission" to take more than 75w, as an analogy it's like a read-only hole on a cassette tape or floppy disk which prevents you from recording data on the medium ... the two wires are just that, a flag telling the video card it's allow to suck more than 75w of energy from the power supply.

 

Quote

Definitely use the 6+2 connectors. Never use an adapter for 6 to 8 pin.

An adapter will simply add those two wires which tell the video card "it's allow to take more than 75w". There's additional losses at the connection point (between adapter cable and the cable from power supply), but that's practically nothing, less than 1 watt of energy converted to heat and a few mV lost due to the resistance in the connector contacts.