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I have a problem with the Corsair HX 1200 PSU. It works perfectly fine with one GPU per PCie cable. When I put a second GPU to the same cable the card doesn’t even start. It’s not a card problem as I switched them and observed the same behavior.

My ressearch told me already to change the button at the back of the PSU to single instead of multipe but It didn’t help.

Anyone faced this issue already or has any suggestions?

2 card on the same cable is too much that's all there is, don't use more than 1 per card.

So with a maximum of 5 possible connected pcie cables you want to tell me that I cannot put more than 5 cards - even if I only put GTX 1060 which would not even reach half of the PSU capacity?

The PSU you have it's 6x VGA power outlet, so 6 cards, i guess with 1050/1060 you can put 2x card per cable, but 1070 or above would be pushing it imho.

That's weird. I don't have this particular PSU to test right now, but I've got a Corsair RM750i and it definitely works fine with 2 cards per cable — I remember connecting 4* rx 480 to that PSU, each card with a single 8-pin connector, and it only has 2 cables (with 2 pci-e connectors each). Maybe something's wrong with the PSU? Do all the connectors actually work?

Yes, its powering 5 cards but if I put the sixth card to the second pcie connector it doesnt power up. The card gets no power whatsoever it actually looks like the card is dead - the system only starts with 5 GPUs. Very weird

I have this same PSU and 6 cards is no problem at all. Have you switched PSU to single rail?

I use Corsair RM1000X powering 7 RX 580, each cable powering 2  GPU, and its stable as hell, with 850w from wall.

Yes I switched it to single and also unplugged it just to be sure that the change is reflected. Still didn’t change anything.
Other than that there is not much to configure. The 850 PSU just works fine with the 6 cards @530 watt, really funny stuff

I use only one GPU per cable also, but connecting two gpu's with 8 pin each shouldn't be a problem, as most cables are rated 300w+.
But for obvious reasons i wouldn't recommend it also.

I have 16 rigs with this PSU, using 3 cables to power 6 gpus.. havent had any issues. What are your power limits set to?

Power limit on the cards? Its an AMD rig all cores run with 1150 Mhz the entire rig consumes 530 Watt ( will be extended in the future). The consumption can really not be a problem especially considering that the 850 PSU just works fine and powers all 6 cards. Just replacing the PSU ends in only 5 gpus starting.

I also don’t believe that the PSU has a technical problem as everything else just works fine ( runs stable for 3 days on a test machine)

Ok so maybe a faulty GPU then.

No, all 6 cards just work fine with the other PSU. Best is really to never touch a rig that is stable you always encounter problems if you change somehing hardware related.

If a 2nd card on the same cable doesn't start, the power pulling is too much and the gpu don't get enough power, are you using powered risers and additionnal PCI power on the motherboard ? it can help smooth the power draw accross all the PSU outputs.

And what you say is true, never touch something that work  8)

GPUs don't need much power to start, it's not like hard drives or anything with a motor, they consume just a few watts when you turn the system on.

True, gpu don't consume much when turned on, but it's weird the GPU doesn't start when it's put in combo with another one, but work perfectly when solo on a cable, maybe there is some sort of protection to protect the PSU or the GPU.

What GPU's OP is using, how many 8 and 6pin power connector per card (which brand/model), what does he use to separate the power (Y cables ?)

They are all Sapphire RX 570 cards (6) and working with only the 8pin connector branched. Pcie powered with a different power cable for all of them.

Separating power was not necessary as I only connect the second 8 pin connector of the PSU cable to the second card and it was working fine. As I previously wrote with the 850 Watt unit everything works perfectly fine.

I see,

Well never tried to connect only one power input of a GPU, there is obviously something blocking you to do this, you probably need a Y cable to double properly the connectors, and plug all of them. I don't use AMD cards. but there is something blocking you, does the rig make the POST properly ? you crash @ windows start right ? did you tried safe mode to see if it crash too ?

No its not crashing the 6th card is just not powered. I can start mining with the 5 GPUs no issues there everything very stable.
I have to check if some Y cables were included but this is just so weird. And obviously shutting down the rig and trying to solve this problem is annoying and downtime which is never good.

You must have a problem somewhere as all my rigs use the Hx1200 and i run them all with 1 cable running to 2 GPU's. I have never seen a problem nor heat issues on the cables.

Could be just a bad cable or connector. Did you test every possible configuration? You've got what, 4 cables with 2 pci-e connectors each? And 6x connectors on the back of the PSU (they all seem to be interchangeable and should work with both the PCI-e and the EPS cables). That's quite a lot of possible combinations — did you try them all? You still should be able to power 6 simple rx 570 cards with that beast of a PSU. You've got 8 pci-e connectors in total, and only 6 cards, so 2 extra connectors. But you're running 5 cards, so using only 5 of the available 8 connectors. Does this mean that neither of the 3 remaining pci-e connectors works?

Anyway, there are eps=>pci-e adapters out there that you could buy, your PSU has two eps cables so I assume you're only using one of them and you could always attach one of those adapters to the 2nd EPS connector and power a couple more cards with it.

Yes, as I wrote if I only switch the PSU unit (nothing else!) leave all cables as they are only 5  GPUs powrt up. If the power port on the PSU would be faulty than 2 GPUs would not work but thats not the case, really hard to say.

But you've got 8 pci-e connectors in total, from 4 cables, and 6 GPUs. Did you try them all or did you just connect one cable, that didn't work and then you started this thread? You're not describing your problem with enough details. There's quite a lot of different combinations available when you've got 4 cables, 8 pci-e connectors and 6 GPUs. Did you try them all? How did you even connect 5 cards anyway if the HX1200 is supposed to come with only 4 pci-e cables? Did you take the 5th cable from another PSU?

Assuming you took the 5th cable from another PSU, you've got 10 pci-e connectors then. Do your 5 cards work with either of the 10 connectors from the PSU, or do they only start when connected with the first ones on the cable (closest to the PSU side connector)?

That's the PCI-e cable for your PSU:

http://i67.tinypic.com/hrheeh.jpg

You're using 5 cables now to connect 5 cards. Are you using number 1 connectors or number 2? Do all 10 connectors work with only 5 GPUs? Or you do you have to use only particular connectors (1s or 2s)?

Stupid things work sometimes, did you try reinstalling the drivers? If the GPUs are good and the PSU and cables work, it probably isn't hardware related

You can't install a driver for something that isn't even recognized by the operating system. His 6th GPU simply doesn't start.

It clearly is a problem with the PSU.

Setup 1 was running for months - no issues:
6x RX 570 powered by one 850W PSU the rig consumes 530W

Setup 2: The exaclty same as above just replaced the PSU with a HX 1200 and had to switch the mainboard power connector - all other cables remained the same.

Only 5 GPUs start the 6th wont even start - it is powered by the second 6+2 pin from the power canle. As the other GPU powered by the same cable works it cant be the cable. As stated above on the same cable the second card was working fine.

And if you put 2 gpu on the same cable, if you disconnect one of the card, it start right ? only 2 gpu on the same cable make one not starting, also in the power supply "chain" is the GPU not starting the one at the end of the chain ?

https://i.imgur.com/fuBCtoo.png

In this little schematic, following scenario

All connected - which one of the gpu doesn't start ?
6+2 pin 01 or 02 disconnected, does the GPU start ?
Swaping 6+2 pin 01 or 02 between gpu 01 or 02, does the GPU start when only one connected ?

As stated before do you use the same power cable and power output of the PSU ? did you tried swaping them ?
Also have you tried to use a molex to 6pin adapter to see if that 6th GPU would start ?
Also have you put the PSU in multi-rail mode ?

I'm dissapointed in this PSU too. It has very stiff wires. And the wires warm if I connect just GTX1080 (180W) with 8+6 pin power by one PCI-e cable from PSU (It has two 6+2 output connectors from single PSU outlet). Warming is not critical but wires of my PSUs of other brands don't warm at all. So now Corsair is just my test and reserve PSU

Thanks for the feedback everyone. I will probably only have time on the weekend to tinker around - the rig is running perfectly fine with the old PSU.
I will keep you posted hopefully with the solution :)

After switching back the HX 1200 unit to the AMD rig it just worked fine.  I didn't change anything just replaced the PSU unit and left all the power cables where they were before (besides swapping the MB power cable).

Funny thing now is that I installed another GPU via the M2 slot - at first Windows detected the new GPU but I had to reinstall and now it is all messed up.
Screen stays black I can't boot from the Boot ready USB Stick - I have no idea how to fix this besides reinstalling from scratch. Did you guys encountered this already?

Edit: Windows is not fully booting up as I am not able to connect with Teamviewer. I suspect this is a graphics driver issue, searching for the topic returns many hits but nothing really useful.

Ok disabling 4G - cleaning the drivers, reinstalling them patching them and turning on 4G again solved the issue. Just Windows that wanted to go nuts. Now the additional card in the M2 slot also works like a swiss clock :)

Thanks everyone for the help - appreciated!