Several GPUs not recognised in mining grid

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frederikvanderveken

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Dec 3, 2017
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A few days ago I built my first mining grid, but I don't succeed in getting all GPUs recognised.

This is my setup:
- ASRock H110 Pro BTC+ motherboard
- 6 GPUs (I will expand later): two RX 570 and four RX 580, all Sapphire Nitro+
- PSU is Corsair HX1200i
- Celeron CPU, 4GB ram
- Lubuntu 16.04

I tested all cards separately in the 16x PCIe slot and each of them is working fine. However when I check the installed cards in OpenCL (
Code: 
clinfo | grep RX
) it never lists all six. Generally two or three are missing. So one of the obvious things to check is if some of the PCIe risers are faulty. However, I don't know how to find the faulty one, as every time I change something, other cards will not be recognised.

It feels extremely random: in one case both the RX570 were recognised but only two out of four RX580. So I unplugged one of the RX580 to check if this might be the faulty riser, but then suddenly one of the RX570 is no longer recognised (while I didn't touch them). And this happens even when I add the cards one by one.

Every GPU is connected with an 8 and 6+2 connector, each on a single rail to the PSU. Furthermore, the risers are connected via a 6 pin to SATA adaptor, three risers on a single rail. The motherboard has its two standard ATX power connections, as well as three extra power connections (two molex and a SATA) for the PCIe slots. I would be extremely surprised if power would be the issue; most 6 GPU rigs I found on the internet had PSUs less than 1200W.

Did anybody experience this behaviour before? I am at loss here, I spend the whole day today only debugging and looking on internet for solutions, alas to no avail.

Thanks in advance!
 
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AnonymousAndy

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Dec 18, 2014
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Have you tried uninstalling/reinstalling GPU drivers with all cards connected?



This portion needs clarification. Do you mean that you are powering three risers with one SATA cable? That is too much current for one SATA cable, you're going to start a fire. 2 is absolute maximum, and even 2 is debatable. Try just 2 per cable see what happens.

 
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frederikvanderveken

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Dec 3, 2017
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I am indeed powering three risers with one cable (it is a 6-pin PCIe cable that goes to 4 SATA connections of which I use 3, like this cable http://i.ebayimg.com/00/s/MTQ4OFgxNjAw/z/RRgAAOSwzaJX2x7F/$_57.JPG). But the GPUs are directly powered to the PSU, will they still draw so much power from the slot?

And afaik this cannot be the reason why the cards are not recognised, because I am not mining yet; the cards are idling, but maybe I'm a bit naive :).

I cannot try yet to maximally put two risers on one SATA cable because I'll need to buy another cable for that first.

My PSU has six 8-pin outputs and six 6-pin outputs. This is how I set it up:

6-pin:
- one 6p->SATA cable to power the SATA port on the mobo and my SSD
- one 6p->molex cable to power the two molex ports on the mobo and my case fans
- two 6p->SATA cables to power the six risers
- two 6p->molex cables, which then use 2molex->8p and 2molex->6p adaptors to power two GPUs

8-pin:
- one 8p->8p cable to power the mobo (ATX CPU power)
- four 8p->8p+6p cables to power four GPUs

And of course the 24p ATX power connector.

I have one 6p->SATA cable left but no free 6p slot (only an 8p slot).
I also have one 8p->8p cable (with CPU written on it) left. I don't know if it is wired the same as a 8p->8p+6p cable, but if it is, I could connect one of the two GPUs that use the molex adaptors with this cable instead, thus freeing a 6p slot. However that GPU will then only have a 8p connection to the PSU (and not the extra 6p).

What do you think? Is that 8p->8p cable usable and will the GPU still get enough power? If not, I'll have to buy an extra 8p->8p+6p cable.

Thanks
 
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frederikvanderveken

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Dec 3, 2017
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By the way, all six GPU fans are spinning.
Does that mean that all risers are ok (not faulty)?
Because if I remove the 1X part of the riser from the mobo, the GPU fan won't spin after reboot.
Or is that too naive?

Thanks
 
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AnonymousAndy

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Dec 18, 2014
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I didn't see you mention if you had tried uninstalling/reinstalling the GPU drivers with all cards installed.

I am sorry, I do not know the answer to most of the questions you are asking.
But you are correct, with the GPUs in idle there is little risk powering 3 risers per cable. But you absolutely must NOT apply load to those cables with 3 connected, they will melt and burn for sure.

I do not know if the CPU 8pin cable is the same as a VGA 8pin cable.
 
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fahadiqbal.shirinkhan

Jun 15, 2018
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Hi, did you find out what was causing this issue? I am having a similar issue (not exactly same) and for the love of me, I am unable to debug it. Apparently a random card disconnects from the motherboard at random times...

Also I have come to find out that some cards are designed to have their fans spin without receiving a turn on signal, you could have those variant so fans spinning would not be an indication of a connection to the motherboard.

Please share your experience!!
 
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frederikvanderveken

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Dec 3, 2017
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Hi, yes I found out. It were the risers after all, low quality. The problem was in the small parts of the risers (those that enter in the motherboard), and there were two issues with it: 1) the pcb is a bit too small, making that the part can wiggle in the PCIe connector on the motherboard (sometimes interrupting the signal), and 2) the pcb's front and back side weren't properly aligned (the copper tracks should be in the same spot on both sides, but there was a shift of a few mms between them).

Out of a set of 10 risers I had, only 4 were usable. I solved it by buying another set from a different manufacturer (of which two weren't that good either, but I still had the 4 good ones from the first set).

Cheers!
 
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