Can I run 1080 Ti (250W TDP) with only an 8pin connection (225W)?

[AndroAsc]

I have a Dell T7910 rig that has 3 x 8-pin PCIe connectors. My understanding is that it provides 150W and the slot provides 75W. I honestly don't know why I don't have more PCIe connectors, it's a 1300W PSU, but that's all I have.

I currently have 3 x 1080, my plan is to change the configuration to 1 x 1080, 2 x 1080 Ti. Specs says each 1080 Ti max TDP is 250W. Can I risk it and use a 8-pin PCIe per 1080 Ti (I will use a 8-pin to two 6-pin splitter and connect both 6-pin and the 8-pin respectively).

Also because my 3rd GPU is a plain 1080 with a TDP of 180W, my average draw per GPU is 226W which is about 225W per PCIe connection.

 

[AndroAsc]

An alternative I can think of, is to underclock the 1080 Ti a little so that it doesn't exceed 250W usage. Will that work?

 

[Eximo]

They are quite conservative with the power delivery numbers on the wires.

an 6-pin connector has two 12V positive lines, rated at 75W.
an 8-pin connector has three 12V positive lines, rated at 150W.

In reality, depending on the gauge of the wire, they can handle a lot more current than that. With a 1300W power supply I don't imagine you will have any trouble powering all of them. Just make sure you get some quality adapters.

Even with a conservative estimate an 18 gauge stranded wire at 12V should be able to handle more like 60W. An extremely long wire would be able to handle less due to internal resistance, but inside a computer that isn't much of a factor. Warm wires will cause a little more voltage droop, which is what they are trying to avoid, excess heating on the wires.

 

[13thmonkey]

What 12V current can that PSU supply.

 

[Eximo]

What 12V current can that PSU supply.

Short answer, enough, long answer, it will be noisy. They are massive flatpacks with a pair of 80mm fans. (Actually they may be smaller than 80mm, I don't have a ruler with me)

I believe Dell only hands out the 225W rating by saying up to 3 GPUs supported, but the tower also can sport a pair of 145W CPUs and 16 memory sticks.

 

[Eximo]

I can go slide one out of a machine here in a few. Happen to be returning one with a dead SSD.

A glorious ten 18A rails, with a continuous supported rating of 1300W across all rails.

 

[AndroAsc]

I don't know. I can't find any proper specs of the Dell 1300W PSU. The "specs" (product sheet) did say 225W per PSU, which is consistent with 75W board and 150W 8-pin.

 

[Eximo]

I don't know. I can't find any proper specs of the Dell 1300W PSU. The "specs" (product sheet) did say 225W per PSU, which is consistent with 75W board and 150W 8-pin.

A glorious ten 18A rails, with a continuous supported rating of 1300W across all rails.

 

[13thmonkey]

that is a sweet amount of power