I have some 8 pin to dual 6+2 power cables and 6 pin risers which are currently connected with sata. I wondered if it would be safe to plug one 6 pin into the psu and the other into the riser, and just not use the 8 pin as I don’t need it in this setup, would this power the riser by the 6 pin. Is this unsafe at all? I don’t have a spare 8 pin to plug it into, hence the question, seems like it would work to me but wanted to check if anyone does this before I set my rig on fire. Also, the cables did come with the power supply, so they must be rated correctly, it’s just whether they will work in this manner or if they only work by plugging the 8 pin into psu. Thanks,
The very short answer is No, it is not safe.
You can plug the 8 pin into the PSU and use the dual 6+2 pin on the other end on two risers (one in each)
If your card only needs a 6 pin and the riser has a 6 pin. Then they both can draw up to 75w. The 8 pin slot can handle that safely. You could also power 2 risers with that 8 pin cable. But if you are trying to connect one 6 pin y connection at the psu and the other 6 pin at the riser, it is not designed for that. Even if it does work I think it would be unsafe.
Safe power to risers only comes from 6 pin direct from psu or Molex from psu. All those riser with a 6 pin or Molex connection and adapter to sata are technically unsafe and a fire hazard. Sata is rated for only 54w. The pcie can draw 75w. So unless you know your card draws less than 54w, even sata is not safe long term. What a lot of people fail to understand is that overloading the wires and connections will wear them down over time. So just because someone has been running one for X months does not mean it’s safe.
For reference the GTX 1060 at is TDP of 120w Will draw about 62w from the 6 pin and 58w from the riser. So above the sata rating. More power Hungary cards can draw more. So unless you are reducing power draw a lot, it could be unsafe.
Most direct sata to sata connections on the riser should be ok if a person is reducing power. More than one riser per sata is not safe long term. I suspect over the next year or so we see lots of rigs or houses going up in flames. Use Molex or 6 pin for risers. Sata was never designed for powering graphics cards. Certainly not 24/7
Ok thanks, would be safe if I had two 6 pin male to male cables and feed two risers from two outputs on the PSU, so each has its own line direct to the psu?
I am just trying to avoid sata and molex as I have two spare 6 pin outputs on each psu and I only need to power two risers with each psu. I can’t seem to find 6 pin male to male connects so readily, let alone branded the same as the PSU, so just been looking if there is a way to use what I’ve already got.
The whole thing stems from that I’m using 1080ti’s, two per PSU, but if I try to clock them anything more than 190w, one crashes. I just changed the main cables to the type 4, official corsair ones, but it still crashes anything above 190w, so I am wondering if its because of the risers.
The PSU is 850w and I have two 1080 ti’s and the rig powered by it, which is about 130w. I’m only looking to get a stable 200-225w per card, not overclock. I am wondering if my PSU is insufficient, but before going through that whole buying experience I want to see if powering the risers properly will make a difference.
6 pin only cable to 6 pin psu would be safe. But finding those cables can be hard.
IF the PSU has a 8 pin slot you need to plug an 8 pin cable into it. If the psu has a 6 pin slot then you plug a 6 pin cable into it.
in case the next question is about the cpu slot on the psu, No I would not use the CPU slot on the PSU to power a riser
I was still editing my other post as you replied. Next question in there 
1080ti GPU’s If you have plugged in both power cables into the GPU you can:
#1. You can power 1 riser with one dedicated cable for sata (just 1).
#2. You can power 2 risers with one dedicated cable for molex.
#3. A 1080TI GPU run’s 235w to 255w stock
You need to run a single gpu and see if you can run stock settings. 100% power, no core or memory overclocking, straight stock. If that runs fine, add your second card. If when you add the second gpu the only way it works is to reduce the power then you have a faulty psu. An 850w psu should be able to handle the 680w for the system you are asking
The biggest issue is that most psu don’t come with 6 pin male to 6 pin male. They also don’t come with a lot of Molex. Since each psu is different you can’t really by generic cables. There are no 6 pin male to 6 pin male for most branded psu. What I have done is go to cablemod.com and custom ordered Molex. I use all 4 labled sata 6pin slots plus the 2 labelled pref. They are all 6 pin to molex direct to the riser. All are on the same rail in my psu and will support the 75w draw of a riser. It’s a pain to have to order extra cables, but so is my $4000 rig or house going up in flames!
Thanks for the feedback. I have two of the same PSU, each powering the same amount of cards. If I try to run the other one stock, it also does the same thing, one of the cards crashes.
So I basically need to use the molex cable, but all the molex to 6 pin adapters that I’ve seen require to be fed by two molex, is this correct? So I can run one molex cable which has four molex outputs, and then two of the molex off that master cable to 1x 6 pin, so I’m basically using four molex feeds to power the two six pins, but all four of those come off that master molex which goes back to a single 6 pin on the PSU?
I personally would never and will never use an adapter to convert anything to power a riser.
Also make sure the PSU that is powering the GPU is also the same PSU that is powering the riser
While I agree that it’s a better practice to power the riser and the auxiliary ports on the card from the same supply, it is explicitly allowed by the PCIe specification. In fact you can power each plug on the card from different supplies. There’s little sense in doing so - you still only operate the cards when all are on or all are off, but there is no safety concern as many would suggest.
Source for the above statement. This is an excerpt from:
PCI Express® 225 W/300 W
High Power Card Electromechanical Specification
Revision 1.0RC
So the simplest answer is to just buy Molex risers instead of 6 pin, and power them from the Molex cable that came with the PSU.
I would guess that most people power their systems via the sata cable and some type of adapter. While this may work for awhile i can tell you from experience in electrical work, over time it can degrade the components until one day it catches fire. How quickly it happens is dependent on a lot of factors such as wire gauge, quality, component strength, how much over the rating you are going. Too much current for a wire generates heat, heat then destroys the lines and connections. Then there is a fire. It’s the same with you house. If you run your rig on a 15amp circuit, the max safe continuous load is NOT 1800 watts it is 1440 watts or 80%. Over time something will fail.
Anyways. Best practice is to not use adapters and power the risers directly from the psu 6 pin best, Molex ok, sata if you have a lower power draw. The 1080ti should not be on sata. Those things use lost of power. If you need more cables you can go to the one I use cablemod.com there you can custom order cables for your exact psu. Their cables are awesome, but the shipping is pricey.
Also, try to buy risers that have 4 capacitors and all 3 power slots (sata, 6 pin, Molex) makes life easier.