Question PCIe risers for mining, potential hazard?

joeacejr15

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Jul 11, 2018
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I heard that SATA can only provide 54 watts max and molex can provide more wattage. Tons of these pcie risers on ebay have sata to pcie x6 for the actual pcie slot that the GPU plugs in to. If I have an rx 580 (I think it's a 180 watt card), and it is plugged into the x8 pcie connection on top, as well as the 16x on the bottom, will the GPU draw the power from the top first, then any residual from the bottom, making the SATA safe to use, or do I absolutely need molex, or does the GPU draw from the 75 watts on the riser first then anything else comes from the 8x connection on top?

The most GPU I would put in here would be the RTX 3080 when those prices come down, but for now I will likely get a few RTX 3070 cards, or some 2080 cards, maybe a radeon V11, or some rx 570's.

Am I overthinking this? Should I just use the SATA or buy molex to x6 adapters for the bottom PCIe riser?

Thank you!
 

TommyTwoTone66

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Use molex. Each card will attempt to draw power from the molex and the pcie bus, but if there is no power available on the pcie bus due to you having 12 graphics cards plugged into it, it will draw all of its power from the molex.

sata to molex adapters should not be used, and will definitely not work for this setup.

I think you may be a little ambitious with your plans also. Most professional GPU miners work with a maximum of 5-6 GPUs per system, I assume there must be some good reasons for that.
 
Up to 12 video cards per rig, and possibly 2x 1200 watt PSU's.
So you don't know what PSU you're going to use?

What I'm getting at... is if the PSU has enough PCIe connectors for all of your cards and enough SATA to power all the risers, their may not be a need to get cables that split an already stressed out SATA cable with four or five more connectors.

Also, the weak point isn't just the SATA connector. You have to take into consideration the PSU and the connector on the PSU side. They probably only use 1 pin for +12V. Is is 16g? 18g? Are the terminals HCS? That's more important than anything.

If you don't even know what PSUs you plan to use, you're asking this question about SATA powered risers WAY too early.
 

joeacejr15

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So you don't know what PSU you're going to use?

What I'm getting at... is if the PSU has enough PCIe connectors for all of your cards and enough SATA to power all the risers, their may not be a need to get cables that split an already stressed out SATA cable with four or five more connectors.

Also, the weak point isn't just the SATA connector. You have to take into consideration the PSU and the connector on the PSU side. They probably only use 1 pin for +12V. Is is 16g? 18g? Are the terminals HCS? That's more important than anything.

If you don't even know what PSUs you plan to use, you're asking this question about SATA powered risers WAY too early.
I'm thinking 2x evga p2 1200 watt, corsair hx 1200, or superflower platinum SE. Whichever is in stock. Good point about the SATA connections possibly not being needed, but I wanted to use them, ONLY if they were safe, to provide the PCIe x6/x8 to all the GPU's directly, if it was safe to do so. Any good PSU's that have tons of PCIe connectors or did I make a good selection here?
 
Well, if you use the stock cables and not extenders, you should be fine if you're ONLY providing power to the riser and not using SATA to PCIe to supply power to the 6-pin and 8-pin connectors on top of the cards.

The pin on the PSU side supports 11A. So 132W. So even if the SATA supports 54W, you're only going to want to use 2 SATA connectors per cable. Use three and you end up with this:



A PCIe slot is supposed to support up to 75W. So there is a rub there. And will the riser still draw power from the slot AS WELL AS from the connector on the riser itself? Depends on how they designed the riser. Without knowing if there's power pins on the riser, there's no way to answer that question. This should be easy to check once you get the risers, though. Use a DMM set to continuity. Put one probe on the +12V on the power connector on the riser and the other probe on the +12V pin of the connector that goes into the motherboard's PCIe slot (+12V should be the first three pins on the left towards the back of your case). If the DMM says there's continuity, then you're getting power from both the slot and the power connector and 75W shouldn't be a problem.
 

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