Puzzled about powered risers

Hi All.. I've built a rig with an AsRock H81 BTC motherboard, 5 x RX480s on powered risers with an EVGA 1000W (GQ) powering the lot. It all runs fine so far.

Each RX480 is powered back to the PSU with a 8 pin to PCI-E express cable (that plugs into the top of the graphics card) and connected with one of these risers: https://www.amazon.co.uk/gp/product/B01ER2Z1GY/

I have the molex to sata power connector that comes with the riser plugged into the molex on the riser and then the SATA power connector attached back to the 6 pin SATA on the PSU. I'm powering two RX480s with one "cable" back to the PSU. - equivalent to the cables that come with the PSU that are like this: https://www.amazon.co.uk/Startech-Power-6-Pin-Express-Adapter/dp/B007Y91B80/

I've read some horror stories about SATA power connectors melting and could do with some advice:

  1. Should I be using 6 pin power to molex cables straight into the riser boards? If so, what is the name of these cables as there seem to be lots of variants.

  2. If Yes to the above, is it safe to have two RX480s off a 6pin power to split molex cable?

  3. Or should I change to having one 6 pin to sata power to molex into the risers rather than having two graphics cards off one cable?

Everything is running fine on the rig, RX480s about 75C @ 35% fan and nothing overheating so far and cables feel quite cool. But once winter is over I don't want stuff to start melting!

Any advice appreciated!

Never ever use thos sata to molex cables , thay arnt designed for such wattage and current , simply put they are fire hazard. Always use direct cables from psu to molex and preferably not more than 2 raisers on one cable. if you know exactly what kind of wire is used in thos psu to molex cables from particular vendor , then sometimes its ok even 3 risers .. but throw thos sata2molex cables out asap.

not the latest info , but that will give you some insight about http://www.playtool.com/pages/psuconnectors/connectors.html

I have red the same stories. But it works like this.

There has been some melting cables while using 2 PSUs per rig, where some raisers were connected to the first, and the others to the 2nd PSU.

I do use the ASRock H81 aswell, and my setup is like this.
PSU1 is connected to the mainboard, also with the additional molex connectors on the mainboard. PSU delivers power to 3 GPUs as well as all powered raisers. (I dropped the SATA connector and used molex instead)

The 2nd PSU delivers power to the last 3 GPUs and the harddrive.

Both PSUs are spliced together at pin PS_ON# so they start simultaneously when powering on the rig.

As you use only 1 PSU, there is no problem in connecting everything to it.
The melting cables were caused by a feedback that occurred when the PSUs were powerd on after each other.

@mo35

is it safe to power 3 risers with one 16 AWG molex cable?

16 awg should withstand 35 amps,

thanks

Yes, that is no problem. I use also 2 modular cables for 3 raisers each.
The GPUs don't draw that much power through the PCIE slots (raisers) so you should be good.

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I have 2 RX 480 running on sata power with temp sensors to test if there is a problem and it seems to be no issue of them getting hot.
They the same temp as the ones connected with a molex cable.

I assume the problem is with older cards like R9 which draw much more power then the RX 480?

16 awg is good , it should handle 3 risers without any problems

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there is rather detailed discussion about powering risers , whats good and whats not , dig in.

Yeh I have been using sata connection for risers for a year now with no issues with rx series I think the issue was with older cards drawing more power,I never use more than 2 per riser

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Any estimation on how much power a riser can draw? 20w? 30w? Is it more or less the same in any card type (290x, fury, 480...) or are there significant differences?

A simple question, you only connect that pin, the PS_ON#? Because I see that the ground need connect too..

Look this.. http://www.jonnyguru.com/modules.php?name=NDArticles&op=Story&ndar_id=27

This is useless? http://www.frozencpu.com/images/products/main/cpa-167.jpg

It's been awhile since I looked it up, but I believe the PCIe specification allows for up to 75 watts to be drawn via the PCIe slot. So the absolute worst case is your riser would need to supply 75 watts, or ~6.25 amps at 12 V.

Most modern cards will draw the majority of their power via the auxiliary power PCIe connector on the card and only a fraction from the PCIe slot, so the more realistic range would probably be in the 20-50 watt range through the riser. This would still require up to 4 amps @12V, thus why most people do not recommend using the SATA connectors as they are only rated to deliver around 4 amps max.

So while using a SATA connector on a GPU tweaked to sip power you might be ok, but problems surface when trying to use multiple SATA connectors per leg off of the PSU and/or if you switch algorithms and the card would draw more wattage through the riser. The 4-pin Molex connector can supply around 10 amps @ 12V, so it is usually better suited to deliver higher currents and is usually why it is recommended to use over the SATA power connectors.

And finally, yes the older cards will tend to draw more wattage via the PCIe slot than the newer ones, but it all depends on many factors. The best bet is to try and avoid using the Molex connectors when possible.

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Hello all.
I have RX 580 with 6+8 pin connection to PS.
Which riser I should use for such connections.
My PS have a 8pin out and riser 6pin in.
This is a problem.
Hope for help.

@imish - where do you buy one of these 16 AWG molex cables? I need one more :slight_smile:

Hello,

I am new here and please for help. I have this) psu.
It has in total 9 PCIe connectors. I will run 6 cards. Can I use the rest 3 connectors to power directly my 6-pin risers?

My concern is that there is no 5V wire and there are three 12V pins in PCIe connector.
So can I power risers directly or not with those PCIe express cables?

Thanks!

OMFG, rewire and power risers from same PSU as GPU before you burned your GPU! https://www.youtube.com/watch?v=c2EDN7xyjZ4