6 GPUs 5850 on one mainboard

[harm]

Hi,
I have put together a mining rig with 6 GPUs (4x XFX HD 5850 and 2x Sapphire HD 5850).

With 5 cards everyting works perfectly, but the 6th one now causes trouble...
It is not the card itself, it is not defect, but maybe the mainboard?

Gigabyte GA-990FXA-D3
http://www.gigabyte.de/products/product-page.aspx?pid=3900#ov
Corsair AX 1200w ATX PSU

I have allready had defect pcie extensions, but the new ones work very good.

My mainboard has four pcie 16x and one two 1x ports.
Conntecting the 6th GPU to the 2nd 1x port my system boots without any problems. But right after starting to mine the 6th GPU lockes up. Well, some times it actually mines 2 accepted shares, but then nothing anymore...

I have switched the two 1x adapters, both seem to be ok.
I have switched GPUs, seem to be ok, too.

My PSU does 1200W what should be more than enough:
6*170W = 1020W + 30W (CPU) = 1050W makes 150W for fans, mainbaord and backup.
Downclocking my GPUs to 500/300 before mining, to reduce power consumtion, doesn't work neither.


Any ideas? Why does the one pcie 1x port work, but not the other one?

[1714804413]

1714804413

[tunatime]

You could be pulling to much wats though the pcie slots could be the board just doesn't like them.  Do this put all cards in the system and see if it boots then try mining just on the 1 card that doesn't want to works and see what hapnes.  If it works you pulling to mich power though the mb

[deslok]

he's right on the too much power for the board they do make extenders with a molex connector in the side. i have to ask if 5 cards works with either pcie 1x slot or only the one.

[harm]

Hi,
thanks for your answers.
It seems to be just the one pcie 1x slot that doesn't like mining. Even with clocks 500/300 on all cards.
Using only this one card at a time I can get it to 700/300 but no more...:-/

I think it is something with the slot...

Does anyone know a working mainboard with 6 pcie? Actually I haven't found an example in this forum, just people intendig to try that.

[BrianH]

Did you try just one card on the slot? Are you using extensions with molex adapters?

[Transisto]

What's the current observed limit on pci-e power delivered from the mobo ?

I am about to push a mobo to 5 without any molexed extender, what is to happen if problem there is ?

I would expect those "double Cu" Gigabyte motherboard to be more able to deliver.

Good luck with your setup, keep us updated.

[bluefirecorp]

As soon as I get a couple extenders, I'll try with my 7x PCI-e motherboard

[jrobe121]

My PSU does 1200W what should be more than enough:
6*170W = 1020W + 30W (CPU) = 1050W makes 150W for fans, mainbaord and backup.
Downclocking my GPUs to 500/300 before mining, to reduce power consumtion, doesn't work neither.


Any ideas? Why does the one pcie 1x port work, but not the other one?

Your forgetting that your 1200W PSU if its 80 Plus certified is only good for 80% of 1200 watts.  Bronze, silver, and other ratings give a little more. Say you have a gold certified at 86% thats only 1032 Watts

I ran 2 5850's and 1 5870 and had a PSU fail to work at 850 watts, needed 1000 watt PSU.  You just dont have enough in your PSU in my opinion.

[harm]

Hey guys,
thanks for your ideas.
Gigabyte support asked me to flash a beta bios on the mainboard. It could be an addressing problem, as only the one slot fails.

I am going to flash the mainboard on monday and try again - gonna keep you up to date;)

@jrobe121
A 1200W PSU does offer 1200W. A efficience of 89 % means it pulls like 1348lW out of the plug to deliver that 1200W. But no name PSU often have problems to deliver constant voltages on the 12V lanes...

Anyway - call you monday:)!!

Cheers,
Harm

[sabe]

My PSU does 1200W what should be more than enough:
6*170W = 1020W + 30W (CPU) = 1050W makes 150W for fans, mainbaord and backup.
Downclocking my GPUs to 500/300 before mining, to reduce power consumtion, doesn't work neither.


Any ideas? Why does the one pcie 1x port work, but not the other one?

Your forgetting that your 1200W PSU if its 80 Plus certified is only good for 80% of 1200 watts.  Bronze, silver, and other ratings give a little more. Say you have a gold certified at 86% thats only 1032 Watts

I ran 2 5850's and 1 5870 and had a PSU fail to work at 850 watts, needed 1000 watt PSU.  You just dont have enough in your PSU in my opinion.

You got it backwards. 1200W means it can deliver 1200W to your components, and will draw even more from the wall because of inefficiency.

In addition, most branded PSUs will happily deliver 100W-200W more than what they are rated for as well before over current protection kicks in. What you lose is some efficiency (80+ Gold PSUs for example may drop to like 80% efficiency when overloaded).

[jrobe121]

My PSU does 1200W what should be more than enough:
6*170W = 1020W + 30W (CPU) = 1050W makes 150W for fans, mainbaord and backup.
Downclocking my GPUs to 500/300 before mining, to reduce power consumtion, doesn't work neither.


Any ideas? Why does the one pcie 1x port work, but not the other one?

Your forgetting that your 1200W PSU if its 80 Plus certified is only good for 80% of 1200 watts.  Bronze, silver, and other ratings give a little more. Say you have a gold certified at 86% thats only 1032 Watts

I ran 2 5850's and 1 5870 and had a PSU fail to work at 850 watts, needed 1000 watt PSU.  You just dont have enough in your PSU in my opinion.

You got it backwards. 1200W means it can deliver 1200W to your components, and will draw even more from the wall because of inefficiency.

In addition, most branded PSUs will happily deliver 100W-200W more than what they are rated for as well before over current protection kicks in. What you lose is some efficiency (80+ Gold PSUs for example may drop to like 80% efficiency when overloaded).

Your absolutely correct, just read a bunch more.  What I said is how someone explained it to me and it made sense for my situation.  I was running 2 5850's and 1 5870 on a 750 watt psu that kept failing, then an 850 which blew up, and finally ran smooth on a 1000 watt PSU.

[BrianH]

Hey guys,
thanks for your ideas.
Gigabyte support asked me to flash a beta bios on the mainboard. It could be an addressing problem, as only the one slot fails.

I am going to flash the mainboard on monday and try again - gonna keep you up to date;)

Harm, counting on you! Please let us know! Would like to use this board myself and I have not seen any confirmations of any other boards working with 6 slots.

Have you tried just one card in that slot to see if it works at all or whether the board is shutting it down when others are activated?

[harm]

Hi,
unfortunaltely I can't confirm that the mainboard supports 6 GPUs.
One of my GPUs slowly died and now I have to send it back and order a new one.
But I can say the slot in question works!!! I am still running 5 GPUs and this time I left another slot free.
So I think 6 GPUs should work. But to be sure I might be able to confirm that in a frew days.

[harm]

working:)