Bitcoin Forum

I have the following setup:

OS: EthOS latest, running fine with 3 GPUS
Motherboard: Asus Prime Z270-P
CPU: Intel i3
PSU: Corsair RM850
GPU's: Sapphire RX850 8gb

The rig has been working fine for months, just received my 4th GPU in the mail.
After plugging it in using this cable https://www.amazon.com/gp/product/B00A45JA52/ref=oh_aui_detailpage_o00_s00?ie=UTF8&psc=1
All I get when trying to power up is a "click" from the PSU, and nothing else.

I disconnected the 4th GPU, and now only running with 3 cards.

Would there be a problem with running 4 GPU's on an RM850 ?

1) If you disconnect another GPU does the new one work?

Yes 850 is enough for 4 GPUs if the TDP of the cards are under 150, example 1070 is 150 TDP, so thats 600 watts + your MB/memory/cpu/SATA power.  Also remember these cards are not using their max TDP when idle, so you should be able to power up into your OS before reaching any power supply max from hashing.  Users can turn the power limit down on their cards before firing up their hashing.  I run my 1070s at 90% so 135w per card
while mining

Your Sapphire RX850 8gb is a 225W rated, so make sure you turn down the power limit before mining...

get another PSU 1000 - 1200 is enough and i suggest cooler master is preferable also try giving risers separate molex cables.

Enabled 4G decoding in bios ?

disconnect all cards but leave one
flash last bios, restart
go into bios, turn off all unused peripherals - sound, serial ports etc.  turn on 4G decoding, all PCI-E GEN options - set to GEN2
save, shutdown
install all 4 cards, power on
install drivers, reboot
you are done

The power supply is not the problem, I use an RM 850 with 5 GPU RX 570. It is quite stable.

I just built a rig with the exact board last night and had the same issue.  The bios needs to be upgraded and a couple of changes need to be made in the bios after you've upgraded it.  Looking for the link to the youtube video that I followed to fix this problem.  Give me a minute.

Here you go ... https://www.youtube.com/watch?v=Z1FnEYI25z0&t=87s

for me PSU is too weak.
try also check other 3 cards.
i have one card with one don't wanna work on some type of risers.

this is a known case, as written above, 4g decoding + pci-e gen2 will solve your problem with a high probability.

The power of PSU should be enough for those 4 cards. Try undervolting and downclocking it if you will have issues with POWER..
And like all of the above posts says, Enable 4g Gen1/2 and rock on ;)

I'm with you on this one, because I ran into the issue last night while building a 6 gpu rig with the same board.  Maybe he could up the power suppy situation a bit, but that isn't going to solve the problem that he is having.  I swapped pcie slots, swapped riser adapters, swapped gpu's.  Everything was working just fine, until I tried to add the 4th card.  Did a little google searching and found out what the real problem was.

Looks like my problem was a faulty PSU, the connector that powers 3 gpu's to the riser, was actually melted in the PSU slot, ordered a new one, installed it, and works perfect now.