Mining rig is unstable with more than 3 GPUs

nebuchadnezzarnebuchadnezzar Member Posts: 3
My rig has been working fine with three GPUs, but when I try to add a fourth, my machine keeps giving me the BSOD when I start mining. I suspect it has something to do not having enough power, but I'm not sure what to do about it.

I have a Seasonic 850W Gold PSU. I'm able to run with three GTX 1060 6GB cards, or with two of those and one RX 580 8 GB. The PSU has three PCI-E cables, each of which one plug that goes into the PSU and two 6/8-prong connectors for GPUs. If I plug each connector into a separate card, it works fine (whether or not that card is on a riser, so the riser doesn't seem to be the issue). But to go beyond three cards, I have to use both of the plugs for separate cards, and once I do that, it becomes unstable.

I thought it might be that the PSU couldn't supply enough current on one connector, but I found that even if I reduce the power target on two 1060 to 50% and then use the same cable for those two GPUs, it's still unstable, even though it should only be using 100% of a normal 1060's power usage.

Other details: I have an Asus Prime Z270-A, with updated BIOS and the most recent Nvidia and AMD drivers.

Any idea how to fix the problem? Thanks!


  • Miner8472Miner8472 Member Posts: 109
    edited November 2017
    What about trying 3 cards and then just using the 2 connectors on 1 cable for 2 of the cards and then 1 cable with just the one connector on the 3rd. Or something like that.

    Try different cards in the main slots to see if it is one of the cards.

    I had a quick look at your mobos manual online and it doesn't seem to need extra power connectors from the one I looked at.

    Are you using powered risers?

  • nebuchadnezzarnebuchadnezzar Member Posts: 3
    Thanks, I tried swapping things around as you suggested. I've got it running stably now with the 3 1060s and one 580 - I switched some cables around, but not sure exactly what did the trick. When my card in the main PCI-E x16 slot shared a power cable, I couldn't get it stable. I also found that one of my risers was bad in the process. When I added a second 580, though, it went unstable again. I swapped that second 580 with a 1070 in a different machine, and now it's stable, and the 580 is now running fine in another machine. But I'd like to get all six cards running one machine. Oddly, I noticed that the RX 580s seem to run faster when there are two in the same machine than when they're in separate machines...

    I'm going to try getting a fourth PCI-E cable or SATA to PCI-E adapters to power the sixth GPU and see if that works.

    Also, yes, I am using powered risers.
  • Miner8472Miner8472 Member Posts: 109
    Interesting. Glad you have made some progress toward getting all 6 on one rig. One fact which may well not be important is apparently if I recall correctly the AMD cards require more power through the PCI-E slots (i.e. the risers) than the nvidia cards or something like that.

    I suppose the motherboard main slot instability issue might have something to do with affecting the power supply to the motherboard itself somehow.

    It really could be something to do with the amount being pulled from risers or just the amount being pulled by the card. You could try making sure the 580 risers have their own cable. Are you using SATA power to power the risers? The power limit is a fair amount lower than molex or PCI-E VGA. Seems the 580 swapping with the 1070 could be a significant clue although it could be driver related somehow.

    I'd personally avoid powering the riser with SATA even though its an incredible headache. This could be a fire risk. I just wouldn't do it if any of the cards pull a lot from that riser, could be a problem. On my PSU molex cables fit the SATA sockets.

    Its hard to say without knowing the cable combos but hopefully one of these bits of info might help.
  • Miner8472Miner8472 Member Posts: 109
    also wondering if 6 GPUs is possible on that mobo chipset. might want to check online for people who have done it.
  • nebuchadnezzarnebuchadnezzar Member Posts: 3
    Yeah, I'm using SATA for the risers. Interesting on this being a fire risk - mind elaborating on why that is? That's the first I've heard of it. The risers came with SATA adapters, so that's the only way I currently have to power them...

    I've seen mention of other people using 6 GPUs on this particular mobo successfully, so it should be possible...
  • Miner8472Miner8472 Member Posts: 109

    If too many amps flowing down the wire, it will get hot. I don't want to say I am sure you will be ok because I don't know. I am just giving you the information for you to make the decision. Generally in terms of ability to deliver power, I understand it to be PCIE (VGA) > Molex > Sata.
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