Problem with asrock h81 pro & RX480 on Ubuntu 16.04

Hi all,

I have problems building my new rig.
Motherboard : Asrock h81 pro BTC R2.0
GPU: 6 RX480 Nitro 4G +
OS: Ubuntu 16.04 LTS server (not desktop).
Installed drivers: amdgpu-pro
No bios update + default settings.
Risers : http://www.ebay.fr/itm/310897618647

When using 2 GPU, all is fine.
After adding the third one, the ethernet is not recognized anymore.

Do you have some ideas ?
- Should i install ubuntu 16.04 Desktop instead of server ? or maybe Windows ?
- Should i install some specific drivers for ethernet ?
- Should i try to modify some settings in bios ? which ones ?

Thanks for your help.
Best regards

i would try to make a suggestion but really the PRO BTC should work out of the box, unless they changed something for R2. .. ofcoarse make sure lanes are on gen2 (I think they are by default though), and set primary display adpater to PCIE/GPU... looking at your risers, i cant see what version they are... what version are they? they look like they might be "not the best" risers... it should say VER 00# on them

you should not need to install drivers for the LAN to work.
I think Server should work, but personally only tried desktop 16.04

I have couple of v2 just arrived noticed they only have one extra power supply going to board v1 has two, will be setting up tomorrow so if I come across anything that might help will let you know

The R2/V2 does have two molex extra power connectors - one is on an edge of the board with the connector facing the side rather than facing up and is easily overlooked - as I did at first.

Show us the results of "sudo ifconfig" and "cat /etc/network/interfaces"

@diamondview thanks I over looked that when checking board last night

Did you connect molex connectors to board or to risers?
My thoughts are either:
- you connected molex to board and not to risers and you get power loss on board or
- you connected both and your board gets too much voltage and something got messed up
Don't use molex that are on the motherboard.

So the issue I had is that ubuntu 16.04 uses a new scheme to name ethernet ports. When changing the hardware, the name of the Ethernet port changes and it is no longer auto configured. This shouldn't be a problem on ubuntu 16.04 desktop, but it is on 16.04 server. The solution is to modify /etc/network/interfaces to match the naming found by running ifconfig.

Thanks all for your response.
I have finally installed Windows and i use claymore, and no problem at all.

I'm just asking now how to handle the 6th GPU because i see 845w max at the
wall with 5 GPU rx480 and my PSU is 1000w.

Thanks...

Yeh you can run cards more efficiently by lowering core clock and under volting GPU but with every new release of software more power is needed, I always Advise to use 1250 watt power supply as minimum for 6 card rigs as you don't want to run power supply flat out, what did you expect rx 480 has tdp 150 watts and was reported to exceed that as well so 150x6=900w you were never leaving any head room with that setup

What watt profit can i expect by under volting GPU ?
I will build a second rig in the next days. What 1250w PSU do you recommend ?

All my rigs run with 1250 watts xfx pro power supplies and super flower 1600 watts, for your requirements the 1250 xfx pro is a good supply and well priced and can handle 6 rx480 was tested on review site and can put out around 1320 watts under load and I have had zero problems with power spikes others are struggling with no restarting and crashing ever

I run my GPU's stock so can't tell you but under volting will not effect your speeds but will cause cards to crash if your core clocks are to high, lower your core clocks then start under volting and push each card till you get it stable at lowest settings then you can add card 6. I would run that rig with 5 cards and use the other card with new rig with beefier power supply

EVGA 1300G2 PSU
I see EVGA used the most with mining rigs

Yes I looked at these but were more expensive than xfx 1250 watts I believe the EVGA are designed from super flower leadex platform and I have 2 of them a 1600 watts supper flower platinum and an 850 watts super flower gold running 2 furys in my gaming rig water cooled 5820k with Asus strix board and 16 Gig of quad channel 3200M/z ram, I always advise to buy the best power supply you can afford as it's most important part of your build in my opinion and will give you a stable rig

The EVGA power supplies are excellent and come highly regarded,any of the supply's mentioned should do just fine

could be, i have a 2000w leadex and a couple corsair ax1200i
EVGA seems to be a good price, ill have to lookl at the xfx but i dont think they sell them here (at least if they do, probably only imports,. evga was that way also until a couple months ago)

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Leadex 2000 watts is a monster no doubt and there top model I think
Corsair are up there with the best I ran my last gaming rig with same

yup, the leadex 2000W is insane, the 1600W is more than enough, but i went all out when building my x99 with 295x2's ... just wanted to make sure i had loads of headroom

corsair is what I use in my other gaming builds

If i divide the total price of a RIG by the number of GPU, i can see that i obtain quite the same result between a 5-GPU rig and 6-GPU rig.
You could expect a lower result with a 6-GPU rig but this is not the case.
This is because of the price of the PSU. Much more expensive for 1250w and over.

The most cost effective is x2 EVGA 850w. And you have plenty of room even if you decide to upgrade cards in the future

I use 2 x 1000 EVGA SuperNOVA G1 in my 5 Fury rig, no problem in last 3 months, + ive got a lot of power to make any upgrades.