Bitcoin Forum

I am fairly new to mining and I am having a mysterious issue I would love some help on! 

I have three rigs, one with 6 MSI RX 480s, one with 5 GIGABYTE RX 480s, and one with 3 assorted GPUs.  They have different motherboards and PSUs.  They are all running Win10, with AMD Catalyst/Crimson driver 16.60.2911.1011.  I am having the same issue with Claymore zcash v12.4, Dual v8.1, and Cyptonote v9.7. 

All the cards are mining, except one seems to mine at %20 of what it should!  The stranger thing is that WHICH card is doing this whimpy mining switches . . .  First it's GPU1, reboot, then it's GPU3, etc~  Also, the issue is inconsistent.  It seems to be doing this about %70, but sometimes I'll get lucky and all GPUs will mine %100 for a time. 

Would upgrading to driver 17.4 help?  Or perhaps a better driver to downgrade to? 

I have tried putting a dummy plug into one GPU, and it does not seem to help, though I have not exhausted experimentation with this. 

Anyone else experienced this same issue? 

Any thoughts/suggestions?

your terminology is fucked up.
never say a gpu mines  at 70% or 20%


lets stay with eth what mh  do you get?

4mh and 7mh  are the common issue number

4mh hook up a monitor  to each   gpu 1 at a time
7mh is  overheating or  weak psu.

next don't dual mine hard    if you use claymore  there are settings for intensity   did you use them?

other questions  what psu's are you using?

what risers do you use?

and the shifting  gpu bug is due to the fact the order of gpus can and do shift with fresh boots.

For Ethereum, my 480's are hashing at about 24MH/s, but there is usually one card in each rig that is hashing around 4.8MH/s.  I say %20, because this ratio stays consistent between the one GPU, and the other GPUs in the same rig, whether I am mining zcash, or monero, etc. 

I will try hooking a monitor up to each GPU one at a time.  This test will work while the machine is mining?  Or should I stop mining in between moving the monitor?  Also, can I use a dummy-plug instead of a monitor?  If this turns out to be the issue, will I need a dummy-plug for every monitor, since the GPU order shifts every time?

I am using platinum EVGA PSUs.  One is a 1600W for the GIGABYTE cards, and the other is a 1200W for the MSI cards. 

I am using these riser cables from MintCell:
https://www.amazon.com/6-Pack-PCI-E-Powered-Adapter-Extension/dp/B01GU94QSQ/ref=sr_1_4?ie=UTF8&qid=1491783885&sr=8-4&keywords=pcie+1x+to+16x (https://www.amazon.com/6-Pack-PCI-E-Powered-Adapter-Extension/dp/B01GU94QSQ/ref=sr_1_4?ie=UTF8&qid=1491783885&sr=8-4&keywords=pcie+1x+to+16x)

Hey there,
I doesn't mine with GPU's and doesn't use that PCI Riser, but if you have the Green Riser, It could be that are some solder points are bad and/or that the Power Chip to handle the 3.3V are false ones.
I have read that in these article, maybe it will help you:
http://cryptomining-blog.com/8595-sharing-some-tips-and-advice-about-pci-e-usb-3-0-extenders/

you have the classic 4mh bug.

which is why I asked for the number in mh.

put a monitor in card one and boot.  see if it goes away

if not move  boot again  see if it goes away


if it is still there after 2 boots mover  it over to card two and boot see if it goes away

same thing boot twice  if it did not work  go to card 3

the 4mh bug is a P.I.T.A  be patient trying to fix it.

btw  it does lower power exactly  on scale so   you don't use full power on the card.

Philip, you're right on point. 

Basically a series of patient reboots seems to have fixed this problem.  In many cases I didn't have to move the monitor at all, just reboot 3-4 times in a row -- checking the hash-rates in between each boot.  Seems like removing the monitor entirely and working remotely with a few reboots helps too.  Also, I had one older card that required a dummy-plug (not even sure what it is anymore!  maybe an old R9?)

A finicky little problem indeed ~ seems to work itself out as the system settles~

Thank you for your help!

When I had a lot of 4 and 5 card rigs  it happened a lot.

Now that i have 2 and 3 card nvidia 1080ti rigs it is a non issue.

Absolutely!  Things got so much easier when I started building 3 card rigs -- Fewer issues and more stability.  And they are cheaper to build!  MB, CPU, PSU all LESS than half the cost of bigger gear~  I don't know why everyone likes to build 6 card rigs ;)  We could make a whole new topic about this!

And yes, the 1080 ti's are very easy to work with! :D