Mining rig 4 Gpu works but 5 or 6 doesn't ??

[gctom]

Hello,

First time poster long time lurker.

I have been mining for some time now with my pc using 2 gpu and everything worked fine so I decided to invest a bit and buy 4 other gpu as well as multiple riser (oh boy was I wrong to fix it would be a smooth upgrade)

Update + Configure bios ... OK
Install GPU + Riser ... OK
Install Windows 10 ... OK

6 GPU are shown and usable with the miner I choose (Claymore or EWBF) but if I use 5 or 6 GPU after 2 min the system reboot (ONLY WHEN USING MINER)
If I use 4 GPU or less EVERYTHING works fine.

My Conf :
MSI z170a sli plus
6x PNY GTX 1070 OC xlr8
Pentium G4400
SSD 120Go Sandisk
ax1200i corsair
6x riser pcie 1x to 16x


What I tried so far :
- Drivers update (368.81 or 382.53)
- Bios Update
- Changing BIOS Conf (PCI-E gen 1, 2 or 3), Enabling 4G on BIOS, Settings Windows 10 conf in Bios
- Changing outlet for Power Supply
- Changing bad riser (all ok now)
- Changing virtual memory
- Putting each GPU on a separate PSU cable
- Putting max 2 riser per PSU cable

But nothing works 

Can anyone smarter than me gives me some input?

[Vaccinus]

if you did everythign to prove that nothing else is faulty, i think that probably that motherboard isn't suited to allow more than 4 gpu, i don't know for sure, but many motherboard can't handle 6 gpu

[gctom]

I changed another parameter in bios : PCI-e addressing to 64 bit and was able to have a 5th GPU running.

So now 5 GPU works but 6 doesn't lmao..
Worst part is that 6GPU works for like 2min before crashing WTF.
It either works or it doesn't but no middle ground.

I know that not all motherboard can handle 6 but I want to believe this one can 

[jpouza]

I`ve already used a maximum of 5 GPUs on one motherboard, the one I use since 2014 untill today (MSI X99S Gaming 9 AC) works flawlessly with 5 GPUs in the PCI-E slots directly (no risers).

I guess you are having some chipset limitations to get 6 cards to work, also re-check the risers connections, sometimes they are the problem.

[gctom]

Hmm chipset seems to be working for other but anyway I tried a new motherboard (msi z270a pro) and same shit!

I can make it work fine with 4 GPU without enabling 4G on bios.

But whenever I enable the 4G to put a 5 GPU my system freeze after 2 min.
And even if I only use 4GPU out the 5 connected.

I tried to find a potential bad riser but since it freeze when I have more than 4 gpu connected I'm not sure the issue is there.


So to summarize :
4 GPU mining, 4 GPU Connected = OK
4 GPU mining, 5 GPU Connected = NOT OK
1 or more GPU mining, 5 or 6 GPU Connected = NOT OK

I refuse to believe I'm the only one to have face this issue 

[steezmatic]

I am having the same issue and tried changing some things in the bio like dmi link speed to gen 1. When I run 4-5 gpu's 1 or 2 of the gpu's drop out. I am also using a corsair hx1200 with rx480 gpu's. I actually have 6 gpu's but one of my risers are out so now I am awaiting better risers and new evga p2 1600w power supply.

[gctom]

Hmm that's weird, 1200w should be enough. At least when I look at my psu thanks to corsair link it's never at full power but maybe yours pump more power I don't know.

Regarding my install I think I messed up my windows install because I saw in another post that activating 4G decoding require windows in uefi and mine is in Bios Legacy.

If someone can confirm?