6 pin 8 pin wattages oh my

[ddbnbbbrsy]

Hi all, we have a Dell T3610 workstation with a 685 watt power supply.

It has two 6 pin pcie connectors on it.

We're testing out an Asus Strix 980, but it requires a 6 pin and an 8 pin power connector..

I've read that per "spec" the 8 pins should supply 150 watts while a 6 pin is only 75 watts.

I've also read that nvidia reference spec for a 980 is only two 6 pin cables.

We are not doing any overclocking, but this system will be used for 3d / "workstation" type work 8 hours a day all week long.


Thoughts? I can't imagine that at stock speed it's pulling all THAT much past the nvidia reference 75 watts on that 8 pin connector. We're using all but one of the SATA power connectors, so I'm a little leery of converting a SATA power to a 6 pin connector.


Thanks

 

[dougp]

The Strix is a custom cooled/PCB solution, this is why it has a different power requirement than the 980 reference from Nvidia. What kind of CPU is it? Single or Dual? The question is how much can the 12v rail supply to the video card.

 

[ddbnbbbrsy]

Single CPU, 6 or 8 core xeon.

I know that these Dell workstation power supplies are known to be very hefty, but there's no way to find out how much amps it puts out of each rail.

 

[ddbnbbbrsy]

http://www.dell.com/support/article/fo/en/fodhs1/SLN290552/EN#Power

"Up to 2 full-height, full length (maximum of 300 W)"

 

[96Firebird]

...but there's no way to find out how much amps it puts out of each rail.

If it shares the same PSU as the T5610, this link shows the amperage of each rail. 5 12V rails, so it is hard to determine the combined amperage without getting that info from the supplier.

Either way, does your PSU show the power ratings anywhere?

 

[ddbnbbbrsy]

It shows this:

 

[ddbnbbbrsy]

It is a similar psu, but for some reason it won't let me post a picture until approved by a moderator...??

http://i.imgur.com/I0aeXVz.jpg

Maybe that link will work

 

[ddbnbbbrsy]

I can see that both of the 6 pin connectors go to a single connector and share the same pin. So I'm assuming that both of my 6 pin connectors combined are *probably* on a single 12v rail, which can handle 18a.

So, we're talking ~216 watts combined.

Technically a 6 pin (75w) + 8 pin (150w) should be able to pull 225 watts.


Hrmmm

Would I be better off using both 6 pins on the power supply to the 8 pin on the card, then splitting a SATA connector to use for the 6 pin on the card?

This particular PC has all SSD drives which I assume have low power draw.

 

[96Firebird]

Yes, very similar.

You have options.

If you have 2 4-pin molex connectors available, you can use those.

If you have 2 SATA power connectors available, you can use those.

However, your best option is 6-pin PCI-E to 8-pin PCI-E.

I'm not a fan of using adapters, but it should work just fine.

 

[Deders]

Remember that the slot itself will supply up to 75 watts of the GPU's power. Seeing as it's an efficient card that won't actually pull the 300w that the slot + 6pin + 8pin is specced to handle you should be able to get away with a 6pin to 8 pin adapter.

 

[ddbnbbbrsy]

Ok, here's the thing though -

I have 2-6 pin connectors that both go through a single 12v rail that will allow for 215 watts. The card has 1-6 pin and 1-8 pin which means it expects 225 watts.

So even with a 6 pin to 8 pin adapter, I'm still overloading that 12v rail by ~10 watts


As an alternative, I use the sata power connectors for the 6 pin. The sata power connectors have SSDs that are pulling less than 8 watts total under load. So it seems like it makes more sense to use the sata power adapters to hook up the 6 pin lead........ And then the existing power supply 6 pins can connect to the 8 pin.

 

[Deders]

Ok, here's the thing though -

The card has 1-6 pin and 1-8 pin which means it expects 225 watts.

So even with a 6 pin to 8 pin adapter, I'm still overloading that 12v rail by ~10 watts

That's not the case. The card will only draw as much power as it needs at any given time. When it is idle the power draw will be under 20W, when it is fully loaded it will under 180W. Nvidia themselves say that the card draws 165W max which is usually pretty accurate.

Up to 75Watts of that (could be lower) will be drawn from the PCIe slot itself. I imagine Asus only put the 8 pin on the card for extreme overclocking. There is absolutely no way that it needs an additional 135W to run at stock or even factory overclocked speeds.

The 75W and 150W figures for each lead are part of the ATX specification for power supplies so that the wires themselves are thick enough so they don't overheat and burn out. The extra 2 pins on the 8 pin plug are just earths. No additional current wires actually needed because the wires should already be thick enough.

The Graphics card connector wires will be 16AWG (American wire gauge) which is thicker than the 18AWG wires that are usually used for the rest of the cables from the PSU. So if you were to use Sata or Molex converters you would want to make sure that you had at least 2 adapters that plug in to 2 different strands coming from the PSU. Otherwise if the whole load goes down one 18AWG wire it could heat up and burn out.

 

[Pneumothorax]

You should be perfectly fine as unless you do a BIOS mod that card and then run Furmark it won't draw more than 200 watts max. AFAIK, only cards like the Gigabyte G1 980 and EVGA Classy can draw more than 215 watts. Just don't o/c heavily and run furmark and you should be fine

 

[ddbnbbbrsy]

Perfect, thank you everyone!

 

[DiogoDX]

Just buy one of these that should work fine.

 

[ddbnbbbrsy]

I ended up using a 6 pin -> 8 pin adapter, ran furmark and the uniengine 'valley' for 30 minutes. No artifacting or other obvious problems.

 

[Deders]

It the heat of the wires you want to check

 

[ddbnbbbrsy]

NM

 

[ddbnbbbrsy]

It the heat of the wires you want to check

The wires were not hot at all.