Finished building my 4 GPU & 2 PSU PC, turned it on but only 2 GPUs are seen in Linux.

After googling you apparently need a add2psu adaptor or doing some DIY modding, which I won't do, to use more than one PSU.

So my question is, do I really need that adaptor or is there something else to do?

What are the wattages of the 2 PSUs?

I use EVGA 1600W to power my Quad 1080Ti machines. I think EVGA will be coming out with a larger version sometime this year.

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Both are 1000W. Wasn't sure how much I needed, so I got those.

Whether you need two PSUs or not depends on the GPUs you are using.
I run a single 850w PSU on my cruncher with three GTX1080, and last time I checked the power drain there was about 400w "spare" and there are no PSU stability problems which you may encounter running near the bottom of the load capacity.

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Bob Smith
Member of Seti PIPPS (Pluto is a Planet Protest Society)
Somewhere in the (un)known Universe?

I have 2 1080, 1 1070Ti and 1 970, guess I could try to see if it works...

I would guess you'd be using around 800-850. The 970 would be the power hog.

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Seti@Home classic workunits:20,676 CPU time:74,226 hours

A proud member of the OFA (Old Farts Association)

Finished building my 4 GPU & 2 PSU PC, turned it on but only 2 GPUs are seen in Linux.

After googling you apparently need a add2psu adaptor or doing some DIY modding, which I won't do, to use more than one PSU.

So my question is, do I really need that adaptor or is there something else to do?

I'm assuming you have each power supply providing PCIe power to just two cards. If all the cards are powered up, then Linux would see all four cards. The reason you only see two cards is that two of the four cards are not receiving power from the one power supply not plugged into the motherboard.

I can see a dangerous issue here. With two of the cards trying to draw all of their required power from the PCIe bus which can only supply 75W max without the additional PCIe power cables needed for each card. You could easily burn up traces on the motherboard if you continue troubleshooting with them plugged in.

All that adapter is doing is providing the "Power Good" jumper on the 24 pin EATX power connector that the motherboard sends to a PSU to turn it on. The electronics is just a relay that is powered up by the Molex 4 pin adapter from the master psu to close the "power good" connection for the slave psu. You could easily make your own jumper or buy one. That part is included with all the EVGA high wattage supplies now. It is commonly used to jumper the power supply on without the 24 pin EATX power connector plugged into the motherboard for custom loop water cooling during the initial filling and purging of air of the loop when all you want to be powered is the water pump.

You can get one at Amazon. XSPC ATX PSU Bridge Tool (24 Pin), Black

The only problem with just jumpering the power good on the slave power supply is that it would remain on all the time. That is what the add2psu adapter is doing by only powering up the slave psu when the master psu is powered on.

That adapter doesn't look all that expensive for what it is. The most expensive component of the part was the pcb fabrication.

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Seti@Home classic workunits:20,676 CPU time:74,226 hours

A proud member of the OFA (Old Farts Association)

I was thinking of making one myself, but for now all the GPUs are on one PSU, will see how it goes.

The problem is now, after installing BOINC, I'm warned:

NVIDIA GPU 3: GeForce GTX 970 cannot be used for CUDA or OpenCL computation with CUDA driver 6.5 or later

Don't know what's up, have installed 384.11 drivers

This is all you need for the 2nd PSU to start up with the 1st:
https://www.amazon.com/PSU-Supply-24-Pin-Motherboard-Adapter/dp/B072JM7KVD

I was thinking of making one myself, but for now all the GPUs are on one PSU, will see how it goes.

The problem is now, after installing BOINC, I'm warned:

NVIDIA GPU 3: GeForce GTX 970 cannot be used for CUDA or OpenCL computation with CUDA driver 6.5 or later

Don't know what's up, have installed 384.11 drivers

Yes, there are lots of solutions for powering up the second psu.

Uggh! I would not use that driver. That one really messed up both Juan's and my systems when it was automatically installed. The current one in the Ubuntu repository is 390.48

Did you install ALL the libraries associated with the main graphics drivers? You need the nvidia libcuda library as well as the opencl library to handle both MB and AP tasks.

I would do a apt-get install purge nvidia* and start from scratch again installing the nvidia drivers.

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Seti@Home classic workunits:20,676 CPU time:74,226 hours

A proud member of the OFA (Old Farts Association)

This is all you need for the 2nd PSU to start up with the 1st:
https://www.amazon.com/PSU-Supply-24-Pin-Motherboard-Adapter/dp/B072JM7KVD

The perfect solution. ;-)

Cheers.

Installing libcuda library and opencl library helped, it's working now. I have btw not had any problems running the 384 drivers before.

I was looking for the Add2PSU adaptor on Amazon, cost about £7 but think it was around £28 to ship it to Denmark...

Try a local System Integrator shop in country. I wouldn't think that shipping from Amazon UK to Denmark would cost that much. You are in the relative EU neighborhood.

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Seti@Home classic workunits:20,676 CPU time:74,226 hours

A proud member of the OFA (Old Farts Association)

This is all you need for the 2nd PSU to start up with the 1st:
https://www.amazon.com/PSU-Supply-24-Pin-Motherboard-Adapter/dp/B072JM7KVD

The perfect solution. ;-)

Cheers.

FYI I just picked the 1st one I saw. Some bad reviews on that particular model but that type of adapter will do the job. It can be made it home as well with some pin extractors, the spare 24pin adapter and solder.

Well I took a chance and did the short circuit fix, or whatever you call it, and it works fine so far... Tried first with only a fan connected to the PSU which worked, so now I have 2 GPUs on each PSU.

My problem is now the the 1070Ti & the 970 is air cooled and the one in the middle gets hot, last I checked it was 86c, guess I´ll need 1 or 2 more hybrid GPUs, if I can find any...

Edit: Now 89c :(

Well I took a chance and did the short circuit fix, or whatever you call it, and it works fine so far... Tried first with only a fan connected to the PSU which worked, so now I have 2 GPUs on each PSU.

My problem is now the the 1070Ti & the 970 is air cooled and the one in the middle gets hot, last I checked it was 86c, guess I´ll need 1 or 2 more hybrid GPUs, if I can find any...

Edit: Now 89c :(

Until you find the hybrids you need to change the fan setttings to increace the fan speed to reduce the temps.
89C is far to high it will slow down you GPU.
There are several ways to do that, the easy way is to run a program who do that for you automaticaly like evga precision does in windows.
The other way it to manualy increace the fan speed in the Nvidia X Server settings.

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Yes with dual slot cards, and the present common slot spacings on anything other than X99 based boards, the middle card in the butt to butt card sandwich doesn't get enough air. A hybrid card in that position is the most common permanent solution.

I just set all the fan sliders in nvidia-settings to 100% each time I boot the systems now. They are always run 24/7 at 100% so why not? To get the sliders active, just run the coolbits tweak once to write to xorg.conf and they will be permanently active.

Looks like EVGA has 1070, 1070Ti and 1080 Hybrid cards available now. Based on my recent experience, you won't find a better price on eBay, in fact you will pay more.

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Seti@Home classic workunits:20,676 CPU time:74,226 hours

A proud member of the OFA (Old Farts Association)

Will try to see if I can get coolbits tweak to work, I'm just worried the lack of space between the cards means it just can't get enough air even at 100% fan.

Will try to see if I can get coolbits tweak to work, I'm just worried the lack of space between the cards means it just can't get enough air even at 100% fan.

Either run the one with the most fans, or the GTX 1070Ti in the middle (as long as it's not a Founders edition; the after market cards tend to have pretty good cooling on them)

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Grant
Darwin NT