I just started testing those risers in the past week, and I’ve been scratching my head about how to efficiently use the molex or the 6pin. When purchasing I attempt to make sure my GPUs are 6+6 pin or 8+6 pin powered, sometimes pricing forces me to get the 8+8 pin GPU
IMO I think you could do option 1 and be safe, voltage wise the cable was built to handle powering 8+6 pin gpu
Thanks for your answer.
Somebody told me that we can’t do this 
Do you know why?
Other option:
What do you think about that?
dont use sata for anything the sata port is rated only 4.5W and could melt
Molex are good 2x risers per cable
optionalny u can use i spare 8/6Pin cable (possibly also use a 8Pin to 2x6Pin splitter) and power the rest of the risers directly…
Ok, the problem is i can’t supply 2 risers with my first cable because there is not enough space between the two molex. Is it possible to add extension? (like that BitFenix Alchemy Black - Extension d'alimentation gainée - Molex vers Molex - 45 cm - Alimentation BitFenix sur LDLC)
If yes i can supply 4 risers with 2 cables (un cable with 2 molex each)
For the 2 others i take photo of my cable :
I can connect the blue one (6pin) to the Riser with an extension (like this : BitFenix Alchemy Blue/Black - Extension d'alimentation gainée - PCI Express 6 broches - 45 cm - Alimentation BitFenix sur LDLC | Muséericorde), the red (8 pin) to the GPU and the yellow to the GPU, right?
Thanks !
Alex
Is the yellow PCI? I can read only “PSU”, what is on the other side? CPU power cable could seem the same but arn’t.
Why don’t you connect red and blue to the grapihc card directly?
Sorry, yes the yello to the PSU (not gpu of course).
The other side is red and blue. Yes i can connect red and blue to the graphic card directly but how i supply risers? (this is why i ask to add extension to the blue to supply the riser with this 6pin)
in case u dont have some spare not used PCIe power cable or molex cable from the PSU u cant safety power the rest of the risers
Contrary to my original post I no longer have ANY SATA cables on my rigs (except the HD). I now make my own cables to power my risers when I am short on cables.
A SATA cable, Connector, or Adapter is rated for 4.5Amps on the 12V rail. The PCIe 3 Specifications allows a GPU to draw 5.5Amps from the PCI bus 12V rail. Therefore a SATA cable of any kind can be over loaded on a mining rig. Do not use them and throw the adapters away.
A GTX10180ti draws 4.4Amps at 80% power (see link in original post). The AMD GPU’s 480 reference cards had an issue drawing more then 5.5amps on the PCI bus and burned up a lot of SATA cables. So again, don’t use SATA cables on a rig unless it goes to your Hard Drive. The old 4 pin Molex connectors (for IDE drives) can handle 11Amps on the 12v rail, so you can power two risers from one Molex cable safely.
So buy risers with either a four pin molex connector or a PCIe connector. Then if you don’t have enough power cables with your PSU either order more or (if you know how), make some of your own.
Hi, very interesting thread. I saw a webpage with specs for cable and they say a 4 pin “molex” max current on the 12v rail should not exceed 5 amp…
Do you have a reference link to know what are the rating for each cables?
here the webpage i saw that: All about the various PC power supply cables and connectors
hi. I read all this kind of info about not using sata to power the risers so I got 6 pin riser and a molex to 6 pin cable for them…2 weeks in and my miner keeps crashing with read fan errors, pc crashing, stalling etc. 2 days of fiddling with changing riser, drivers and clock settings and lots of google time, I finally check the molex plug is in properly only to find it burnt/scorched and slightly melted around yellow cables…so much for only sata being bad…was it only from bad crimping or should I change to double molex to 6 pin.
using 2 zotac 1070 amp extreme (250w 2 8pin)
mem clock at +860 (4762mhz) 75% power now (and the sata to 6pin 
) was set at 890 and 80% power before trouble started
Personally, I plug 6-pin directly from PSU to riser. I don’t use any of the attachments. 0 issues.
Yes, the manufacturer of the connector, pin, and socket (AMP, now called TE Connectivity). The Web page you reference, lists the part numbers and even states a 13Amp / pin capacity from the manufacturer.
However, then the author limits the power to 5 amps for some unknown reason based on accurate calculations. However, the power limit on these cables and connectors is a combination of the connector, the quality of the wire, the length of the wire, the gauge of the wire, and the ambient temperature.
So according to the Electronic Tables and Formulas for American Wire Gauge:
18 AWG wire can carry a maximum of 16 amps. 18in of 18 AWG wire has a resistivity of 9.6u ohm and will drop 0.105 volts at 11 Amps, 12 volts, and will dissipate 1.5 Watts (double that to include the ground wire). So the voltage drop is well within the ATX and PCIe specifications.
To get a handle on the dissipated power: 3 Watts of energy into 1 liter of water, will heat 1C in ~23min. However, we are not dealing with a closed system here and the wire is dissipating its heat to the air. Heat is generated anywhere in the circuit that has a resistance to the flow of electricity (most notably the GPU). However, the wire and connector can also generate heat as they have small levels of resistivity. The connector contacts and its crimps to the wire are specific areas of heat concern. Hence the gold plated contacts on very high end connectors, (gold has a very low resistivity and cannot oxidize).
There is limit on how SHORT you can make the wire in a power cable. Longer wires have more capacity to transfer heat away from the connector and dissipate it, but they also drop more voltage. Short wires cannot dissipate as much heat from the connector but drop less voltage. So a properly designed power cable is a balance between both. The 11Amp specification is relatively conservative given the components involved and can be found all over the Internet. I have included an example below.
However, having said all that. There is nothing limiting a vendor from saving some money by purchasing copper alloys instead of pure copper wires. Buying cheep pins and connectors that generate more heat. Most if not all PSU power cables come out of China and are intended for the consumer PC market. So cutting a few corners will never be seen right?
My point is that ONLY you are responsible for the safety of your mining rig. Watch out for poor quality components and connectors. Most of the off the shelf components we use are not intended for the extreme use conditions of mining. PSU cables are at the top of that list.
If you are overly concerned then buy a crimping tool, some good connectors, quality 18 AWG wire, and make your own cables. It is not very difficult, and cheaper than buying extra cables. Perhaps I should publish a manual on how to do this?
Yes, it would be great you make a manual for making your own cables, I usually have trouble finding specific electrical parts even on specialized big stores(not from the U.S.), having the names/parts of everything needed would be great.
I haven’t even considered all of this information in the past and it’s a bit overwhelming, I can’t see any power supply I can trust now hehehe, but it’s great information.
Thank you very much for the informative thread.
My plan was to start with an 6x 1080 Ti setup. I purchased two of the Seasonic PRIME Ultra 1000W 80+ PSU and a six pack of the risers that have the option for molex, SATA or 6-pin. Each PSU has 3x 8-pin double cables and then 3x 8-pin single cables. Sounds like using that configurdation would be best for the GPU’s and risers. I also have a dedicated 20A outlet that was purposely installed for PC equipment. Hope to be at or under 80% load with 6 gpu’s. Luckily I have a licensed and bonded electrician that will install two additional 20A circuits for $350 if necessary. Let me know if this overall approach sounds reasonable. Thanks!
This is a great thread however I am having trouble following all the finer details. My setup is going to be very basic and used for rendering with mining on the side when not rendering. Maybe you can confirm if there are power connection issues with the SATA connections because it sounds like there could be based on above.
I have a 980w psu (mac pro 5,1) which only has 2x 6pin connectors and I want to use with 1 gpu. If I buy a card rated to lets say 250w, with the 1x 6pin and 1x 8pin, can I connect the 2x 6pin-to-8pin and use 2x SATA-to-6pin?
My worries are:
splitting to SATA - dual SATA theoretically can supply up to 110w, but what if the draw isn’t equal, say all 75w goes to one SATA connection for a period? Or are splitters wired in such a way that its evenly distributed?
2x 6pin-to-8pin - also a splitter which on paper is adequate but maybe I in reality this works differently?
If you need more information I will try to get it. Hobbiests have told me this should work fine but your expert opinion would be greatly appreciated because I don’t want a fire hazard.
Thanks
A 1080ti should never be powered on a riser by sata cable. But your post is not clear if you are putting the card directly into the mobo. If you are, the sata, molex, etc is irrelevant as the card will draw it’s power from the mobo x16 lane.
Now the card itself need 1x 8pin for 150w and 1x 6 pin for 75w. Most people use 2x 8 pin ports on the psu, but one 6pin on the riser does not plug in the extra 2 pins. The total potential draw is 300watts
No I am not using a riser, it is directly on mobo. The SATA connection is relevant because the PCIe supplies only up to 75w for the gpu. I still need to supply an 8-pin and 6pin on the card:
{mobo} 6-pin (75w) + 6-pin (75w) => 8-pin (150w draw) {gpu}
{mobo} SATA (55w) + SATA (55w) => 6-pin (75w draw) {gpu}
Hopefully that makes sense?
No it does not make sense. There is no sata connection on the card. The 75watts comes directly into the card from the x16 pci lane. You will need 2 cables an 8 pin and a 6 pin.
Most psu come with at least 2x 8 pin connectors. Often they are 8 pin for the psu connection them split into 6+2 at the other end.
please check how are the sata connectors you want to use build to be able to sustain the 54W rating 4.5A(3x1.5A) they need to use 3 pins for the positive and 3 pins of the negative lead a lot of these Y converters dosent follow this, another think to consider is that you would use 2 sata connectors so u use 6 pins for positive and 6 pins for negative that means 12 pins and all of them need to be connected perfectly without any flaws making obsolete connection resistance causing unbalanced circuit this can be caused by dirt,oxidation or even manufacturing fail can cause that the pins dosent line up correctly and the connection isnt able to give 1.5A on each pin and now consider to yourself how lucky/unlucky it is to have 1 or 2 pins from 12 not connected properly and if you are ok with taking the risk …btw oxidation will create overtime on every copper or steel pin that is natural but putting the pin under current will fasten the process…another think is your PSU in case it is a multi lead it will have total rating for all SATA/Molex leads and this can be a bottleneck as well new PSUs are almost all single lead some more expensive ones can be switched between single lead and multi lead design
another thing to consider is the temperature the connectors are tested at 25 °C and based on the methodology under full load should not exceed 30°C and as everybody knows the higher the temps the higher the resistance of the material will get so if you let the GPU blow +60°C air on them the gpu will report to PSU that is receiving lower current PSU will try to compensate the lost with pushing more power thru the degraded connection if not already on the limits as well and heaving more connection points (12 in one connection) isnt helping in such situation at all
Are you suggesting they power a gpu with a sata cable connected to some 6 pin adapters then connect that to the GPU main power ports? That has fire written all over it. I don’t know why sata is even being consider when the GPU is going to be plugged right into the mobo
