Molex Power Adapter for PCIE Riser

[fk1]

Hi @ll,

I just received new Hardware today:

- Asus z270a prime
- some PCIE risers UsB 3.0 with molex connector
- 3x 1060
- already owned 3x 1050 ti
- 2x Corsair cs650m PSU

I already connected 5 cards like this:

PSU1 powering Motherboard and 3x GPU PCIE 6PIN including the 3x riser with molex

PSU2 powering seperatly the other 2x GPU PCIE 6PIN plus the 2x riser with molex

now one molex cable of the corsair PSU has 4 molex connectors. I assume I can power 4 riser in total therefore? nevertheless, I can not connect the 6th card to PSU2 because the wires are simply too short.

I got one of these SATAPOWER<>MOLEX adapter in each package of the riser but I have read somewhere it is not recommended to use them because they can catch fire. What do you guys think?

I also searched for old extensions in my garage but only could find another form of SATAPOWER<>MOLEX. It was an extra of an old enermax or bequite psu, what do you think of these?

[fanatic26]

If all of the molex connectors are on one PSU chain you do not want to put that many. It will try and pull 300 watts through one single 12v line. I would recommend no more than 2 risers per chain on the PSU otherwise you have the possibility of melting wires.

[fk1]

Hmm okay but if I put maximum of 2 risers per chain I need to use adapters like stated above because I dont have any more molex chains given. Only one chain / psu were delivered...

e: another question: one pcie cable has two connectors. is it okay to power 2 gpus/cable or is this only for 1 gpu with 2 connectors?

[fk1]

ATM I am planning to do the following:

PSU1:MOLEX Cable: Powering Riser 1&2
PSU1:SATACable2Molex Adaptor: Powering Riser 3
PSU1:PCIE Cable1: Powering GPU 1&2 (6Pin each)
PSU1: PCIE Cable2: Powering GPU 3 (6Pin)

PSU2: MOLEX Cable: Powering Riser 4&5
PSU2: SATA Cable2Molex Adaptor: Powering Riser 6
PSU2: PCIE Cable1: Powering GPU 4&5 (6Pin)
PSU2: PCIE Cable2: Powering GPU 6 (6Pin)

I am still waiting for an add2psu adaptor so I have read I should also connect a fan to the 2nd PSU in case the rig shuts down. I guess I will take an extra SATA Cable for this and adapt to Molex.

I am also planning to observe the temps of cables and asaptor with a temp gun to make sure nothing gets too hot. I still hope someone confirms this is a good idea or prevents me from burning the whole rig/house...

[fk1]

running this setup for 30 minutes now with default clocks/powerlimits. I cant see any problem with the single sata2molex connectors running at ~35degC.

The PCIE power connectors 6pin are hotter running at 44degC so I keep another eye on these but I cant imagine this will catch fire...

[grape_tectonics]

It depends on

a) the gauge of the wire
b) How much each card drains through the pci-e slot

First one is pretty easy, just look at whats written on the yellow wire going into your molex chain probably something like AWG 20 or AWG 18, then consult this chart: http://www.engineeringtoolbox.com/wire-gauges-d_419.html (go by the gauge on your wire and look at the amps noted on single core). Multiply the number by 12 and you have the max amount of watts this wire was designed for.

Second one is tougher but you can assume the maximum any card will drain from the PCI-e slot is 75W since that's the max allowed in the specification.

If you're just gonna test it then most electrical wires are rated for up to 75C, as long as it stays under that at full load, its fine.

[fk1]

So i took a look at the risers sata2molex adaptor and it is 18AWG. So single core 9.5 * 12 = 114Watts max, should be fine.

Now I cant find any AWG on the cables from the psu but afai can say they look pretty much the same gauge as the ones the adaptor is using.

With that information I am less scared to put another fan for second psu as security on one of the SATAPOWER cables. tyvm grape_tectonics

[fk1]

one thing that comes to my mind: I currently use 2 pure molex connectors per cable. in theory it is possible that 2 cards drain a total of 150w out of pcie. but those cards also have seperate 6 pin pcie power connectors. can i assume that they wont ever drain the toal of 75w and if so, what should I expect else?

[iamnoobplzhelp]

I use a server power supply like this to power the cards and the risers for up to 8 cards.
http://www.parallelminer.com/product/hp-1200-watt-power-supply-kit-for-gpu-mining-platinum-94-zec-dash-eth/
Then I use a ~400w PSU for the motherboard and SSD.

You also want to use PCIe 6 pin powered risers, like this:
http://www.parallelminer.com/product/ithoo-usb3-0-pci-express-1x-to-16x-extender-riser-card-adapter-w-24-cable/

Then use a GPU power splitter like this to power both the card and the riser:
http://www.parallelminer.com/product/18awg-pci-e-6pin-to-dual-8-pin-y-splitter-extension-cable-2x-62pin-cable-6in-each-side/

[fk1]

Yeah next time I will also use a server PSU.Unfortunately  I realized this way too late