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I've been running a few mining rigs, which are basically just motherboards crammed with cards.

Due to heat problems, I've been looking to get some risers - and they finally arrived. I got 100 cm flexible USB cable risers, with SATA power. They look impressive 3 filter caps and a VRM on the riser board.

Anyway, the first thing I found was that no cards would be detected on the risers until I set the mobo BIOS to PCI-e v1.0.

So far, so good. So, one at a time, I transferred cards from mobo onto riser cables, and after a few false starts, I had 2 cards running on risers, and 1 on the mobo.

That's when I start to get adventurous, and connect a 4th card to a 1x PCI-e slot, and power it via a 2nd PSU. All the connections are double checked. The riser is in the slot the correct way round, etc.

Link the PSUs with a dual PSU adaptor, and power up.

*Sizzle* *Pop* *Crackle* <Burning smell> Cue sparks and smoke rising from the 1x PCI-e slot. The mobo is totally dead.

I recheck all the connections, and they are definitely correct.

Thinking I made a mistake, I decide to have another go.
This time, I connect directly a 1x PCI-e slot with a 4th card, after triple checking everything.

*Sizzle* *Crackle* Sparks. Another motherboard now dead.

I don't get it. I've built dozens of PCs in the past, and built a heap of mining rigs, albeit without risers. I've done dual PSU before.

What could have happened? What was cause sparks and sizzling and burn out a mobo. I've looked at the PCI-e riser design, and the power pins are not connected on the riser, so I don't see how a power surge or something could have come from the 2nd PSU back feeding the PCI-e slot.

Any ideas? Could it be a bad riser card? I've run a multimeter over it, and there don't appear to be any shorts or anything. I'm completely baffled.

all powered risered card have to be connected to main psu

That is exactly why I only run 3 cards per setup. One psu for the whole thing, no linking a bunch of psu's together, NO POWERED RISERS, 0 problems. These 3 card rigs pay for themselves very easy and you don't have to put up with all the horseshit. I would not have a powered riser anywhere in my house. You don't need them if you don't put 500 gpu's on a 100.00 mobo. Get a good Asus mobo, get one 1050 Seasonic Gold PSU, and 3 280x or 290's or 7950 cards and you will have none of the fireworks, remember, powered risers are not needed at all.

is that true? I thought you could power the riser with the secondary psu as long as you also power the card with the secondary psu. You can't mix.

yeah you can't mix, no powered riser on second psu.

Powered risered cards on psu 1, non powered risered cards on psu 2

Thats backwards man, because the card without powered riser would be pulling a little from the MB which is connected to PSU 1. Therefore, you would be mixing PSU 1 and PSU 2, if you don't use a powered riser seprately.

Don't confuse people on here.

You had too much draw on your board. Do you really have 100cm(3 feet) long risers?

If they are actually that long, your GPUs would pull too hard and that's why you had a burnout.

The only way you could hope to make that work on more than 3 cards would be to undervolt your cards before putting them on risers. If you have them on the stock voltage and software, the card will pull whatever it needs(remember that the power on will momentarily pull max power through every port for POST). If you're on a 100cm riser, you're pulling WAY more than a 1x slot can put out when it's already probably struggling to feed the cards on the 16 pin connectors.

It's a hard lesson but smart people only have to learn it once.

You'll probably have to replace that board but when you do, stick with 3 cards max unless you get shorter powered risers.

I have no idea what you've done, but there is absolutely nothing wrong with powering riser cables off any power supply. I've over 30 7950 or better GPUs in use right now, and half of my rigs split the riser's power source between two or more power supplies.

The noob above me has no business posting. The USB riser cable length has nothing to do with this. USB risers are nothing but powered by design, and no voltage other than data is transferred over the 100cm cable. 12V is provided externally, and 3.3V is generated on that PCB. NO voltage at all comes from the motherboard. They will not work at all unless you power them, due to the 3.3V.

http://i879.photobucket.com/albums/ab357/pontiacg5_2010/1157c52c-25d5-4e00-8c6e-444046d21f86_zps1c23c408.jpg

Running three gpus directly on a motherboard is a really dumb way to mine. Not only will the heat kill most of the cards in no time, the extra heat will draw more power and limit your under volt headroom. Fans burn out fast at 100% speed and 80c temps, and I speak from first hand experience. Look through my photobucket if you doubt me.

 

Off topic, but are your alluminium case custom ones? If not where did you get them, I'd like to buy a bunch of them

Yes, they are completely custom. I waterjet cut them and bent them up myself. I was planning on selling them at one point, but now I'm thinking the margins aren't worth fighting for. I'll just keep mining  ;D

lucky you are!  ;D

Where did you get the risers? Do you have an image of the burnt 1x PCI-E slot? If not, where did the crackle/spark happen?

Got the risers from a Hong Kong vendor.

When I powered up, I saw sparks jump from the 1x slot and heard sizzling (both times). After that, though, there was nothing to see. No burned contacts, no burned traces that I could see. I could smell it though.

I've subsequently reused the "killer" risers, after doing a full electrical continuity test with a multimeter, and verifying no shorts or missing connections, and they work perfectly now that they are powered from the primary supply.

I can only guess that during power up, there was some sort of "ground bounce" problem, which caused the ground voltage on the PSUs to pull apart. I suspect that as the 2 PSU grounds were only tied together by a single piece of 18 G wire on the dual-PSU adaptor, that this was not enough to ensure full equipotential bonding, and that it was the ground current that fried stuff.

Perhaps, if all your PSUs are very strongly grounded together, then you could avoid this problem.

I can see why if the risers are on the same PSU as the mobo, this problem can be avoided. The cards will provide a very low impedance ground plane between aux power input and the 16x slot. This will provide a very strong cross-ground connection between the 2 PSUs. If the card and riser are on the same PSU, then any ground currents have to go through the PCI-e signal and shield wires.

Now we have mobo's designed for mining, now we just need some nice PSU's.

I got into mining and being an IT guy I noticed a lot of the guys in this forum either purposely give bad information, or are really that dumb and stumbled into this to make money and have no real understanding of blockchain tech, hardware, GPU's or power.

Must be the risers, you have done nothing wrong in the text you posted. No curcuit shortage, nothing. Expensive mining rig u got there  :-\ Problems with minin rigs are almost always riser related. What we need is a proffesionall riser company.

As were said above, if you use 2 PSUs then:
Rule #1: Do not mix PSU when powering risers and GPUs: each GPU with its riser should be powered with only one PSU.
Rule #2: Wire both PSUs, rig frame (if it's metal) with strong cable to avoid "ground bounce".
Rule #3: If you use risers, do not plug any GPU directly in MoBo, it is common reason of burnouts.


Just perfect explanation I couldn't make due to problems with technical English vocabulary.

3 GPUs per rig is a waste of space and money if you ask me, but to each their own.

I have never had a single riser burning issue and I've connected over a 100 GPUs to various rigs (6 or 8 cards).

The "secret" is to power risers with molex or pci-e cables and avoid the shitty sata connectors that are just molded on the cables. The real risk is to have 2 cables inside the connector melt together. These connectors and sata cable are not rated for high amperage. Also do not power more than 2 risers per molex cable. Get at least ver 006 risers.

With a good quality PSU (do not go cheap on PSU) you're fine.

And just some basic safety rules: avoid to place rigs near water sources or materials that are easily flammable. I've seen some people on here stacking like 10 rigs in a room on the carpet floor. That's just asking for trouble.

I don't get it how people can manage to burn their rigs when going into mining stuff, you should learn more not only about that fantastic crypto world but also get some knowledge about electronics, power distribution and how does this all works together in theory and whats happening inside of all your machinery... I used to power my risers stright from the PSU without any capacitors, voltage regulators on boards just because its not even needed if you know what are you doing it's not needed at all, chinese just put this stuff on your boards to look nice and make bigger profit of worth nothing electronic components. To long cords, bad connectors and that all make higher resistance of circuit and failure at all, also ground loops, bad grounding which may cause inductions and amperage rise or falling rapidly.


It doesn't even matter if you have efficient PSU, you could even use 12V car battery to power your risers or GPU's, it doesnt matter if the potentials are fine so it belongs on how you connect PSU's together and thats it.

 Thanks, Reagrds.

I was thinking if you put your riser connection into PCI-e slot "Backwards", then it sure burnt it.

see this thread, not sure if it is, and might help in case

https://bitcointalk.org/index.php?topic=1983900.0

I agree, while I don't mix my riser power with 2 PSUs (I use 1 PSU for the board and all risers, the second just to power cards) I do know people that do mix the PSUs and their systems don't fry (why take a chance). 

It sure sounds like a riser put in backwards. 

Try downgrading your system a bit. Follow KISS. (Keep it simple, stupid.)

Maybe start with a dual-on board- system, Using 1 PSU, then add risers/GPUs 1 by 1.

This might help you pinpoint where the fuck up is happening. But might not prevent you from doing it again. lol

^^^ This is a perfect example of how to start a fire either by crossing voltages or one psu crapping out while the other is still on.

*NEVER* power the riser and gpu from different psu's.

*ALWAYS* power the riser and gpu from the same psu.

 The length of the USB cable linking the riser to the "shortie board" that connects to the motherboard DOES NOT AFFECT THE POWER DRAW.

 That is NOT the issue at all.

 Backwards riser - possible but that more likely would cause the system to not power up at all.

 I'm more inclined to think there is an issue with the "add second PSU" adapter - one reason I like the B250 Mining Pro 19-slot MB as it has that part built into the MB and common-links their grounds the easy AND HARD TO MESS UP way.

i killed 2 Asrock H110 BTC Pro because of crap soldering on risers

after checking the whole rig to the point of mental exhaustion and throwing in the towel, i started to check the soldering points on the riser components and sure enough i found 2 pieces (from the same batch) that had fused solder points, after replacing them and buying a third mobo problem solved

moral of the story is dont trust non quality certified equipment and at least do a visual inspect before use

Nothing will happen because there is no potential differences, and however if there will occur a lack of power on some components, system will shut itself down immediately... Also nothing will happen if you lose powering on one of PSU - it will cause the same.

I had many times back to my mining rigs to see that the motherboard is not powered due to PSU failure but the orher one is running still powering risers or GPU's external input or conversely - the cards were not powered but the mobo (system) was running with black screen, but after reboot it was everything OK anyway.

Guys, come on these are not 80's electronics, I know it is chinese crap done for $10 but we still have some protective circuit inside of it.

Regards

One other note: on rig start up sometimes you may forget to run whatever S/W you are using to setup the TDP. This is especially important if you are operating 1080ti's and accidentally forget this step and start at 100% TDP and your rig is laid out for say 65%.

I have no problems with 8x1080ti rig starting and running at 100% or even 110% TDP.
If you mean that if the rig is not cooled enough for running at high TDP, then GPUs will halt upon reaching 94C degrees or whatever temp limit was set.

 Easy to set up LINUX to automatically and reliably set your TDP as part of the bootup process.

 Windows - well, I mostly like Afterburner but it DOES occasionally lose track of settings for one or more cards....