3 x 290s on an Asus M5A99FX - do I need powered risers?

[ozoner]

Looking for some help please folks - advice on motherboard and power draw.

I'm trying to work out whether I can get away with running 3 x 290's plugged straight into an Asus M5A99FX Pro 2 motherboard. ie without powered risers. My cards currently pull around 320watts each. The 8 pin power connector is rated at 150 watts, the 6 pin is rated at 75 watts, which leaves around 100 watts to be drawn from the motherboard - multiplied by 3. Seems like a lot to ask of it??

The motherrboard is supposedly rated for quad crossfire - it has 2 true 16x slots, and 2 x16 slots in x4 mode.

Am I going to kill it if I plug all 3 cards directly in? I see plenty of posts elsewhere saying "3 is the max number of cards you can run without powered risers", but none of them are talking about running cards that draw as much as a 290. I don't want to fry the board or cause a fire or any other such extreme things

Thanks for any input.

PS I am mining scrypt coins.

[repairguy]

I would recommend using at least one powered riser on your 1x slot, without having the board in my hand I can't tell you for sure if you absolutely need it.

[ozoner]

I would recommend using at least one powered riser on your 1x slot, without having the board in my hand I can't tell you for sure if you absolutely need it.

Thanks for the reply. It has 5 slots, - 2 true 16x, 2 16x but wired as 4x, and a single 1x.  I had planned on using both 16x slots and one of the 4x.

I am struggling with physically fitting the powered risers in the case - the cards sit too low to fit them. I am not against powered risers, in fact I'd quite like to use them, it's just not an option in my case.

Thank you again for replying.

[reubes]

I ran 3 x 7970 directly off I think it was an Asus P8Z68-V PRO with an i5 for a few months no problems. I suspect higher end boards rated for quad xfire etc with 4 long pci-e slots probably have beefed up power tracks on the mobo to handle more current as compared to cheap boards which are much thinner and probably not designed to have more than 2 cards max ran off them. Having said that, I would definitely prefer not to do this on my own board for peace of mind, considering burnt tracks will probably get rejected from warranty.

Also I think the max power draw on a pci-e 16x slot is supposed to be 75W?

[repairguy]

I ran 3 x 7970 directly off I think it was an Asus P8Z68-V PRO with an i5 for a few months no problems. I suspect higher end boards rated for quad xfire etc with 4 long pci-e slots probably have beefed up power tracks on the mobo to handle more current as compared to cheap boards which are much thinner and probably not designed to have more than 2 cards max ran off them. Having said that, I would definitely prefer not to do this on my own board for peace of mind, considering burnt tracks will probably get rejected from warranty.

Also I think the max power draw on a pci-e 16x slot is supposed to be 75W?

16x 75 watt

1x  25 watt

Thicker/wider traces and more supply wires to the motherboard is what is necessary. Running 3x 7970 is not the same as 3x anything else. 

Not sure on the warranty. I am curious,Has anyone here rma-ed a board that burned because of too many gpus?

[atp1916]

I would personally go powered risers to provide the extra watts.