PCIe Cards Working Randomly

[Marekkon5]

Hello, I have 3 r9 280x (Gigabyte).
- One is in case, in PCIe x16 Slot working fine

For the other two I have 2 expanders, and two slots (PCIe x16 and PCIe x1).
Because the GPUs wont fit inside and it would be overheating both must be on expanders outside case.

I tried all combinations of plugging those cards in those slots but none work as intended.

- Either only card nr.1 worked (0 - Internal, 1 - 1st external (PCIe Expander 0006), 2 - 2nd external (PCIe Expander 0007s))
- Or all showed up but system completly froze. (Only force restart helped)

Each time I swapped, it did one of those.

What can be causing the problem?
Too weak PSU (EVGA 850B, those cards have 300W TDP Each), or
Cable, expanders, or something else?

(BTW Cards are working fine if connected only 2 at the same time)

CPU: Intel Celeron G3900 (2 Core)
MoBo: AsRock B150M Pro4S
RAM: 1x CRUCIAL 4gb (there is only one supported type: http://www.asrock.com/mb/Intel/B150M%20Pro4S/?cat=Memory&Model=B150M%20Pro4S&Vendor=Crucial)

Thanks.

[1715564556]

1715564556

[1715564556]

1715564556

[0xcosmos]

get some risers
connect all gpus to risers
switch x1 and x16 lane speed to gen1 in bios

[leonix007]

Hello, I have 3 r9 280x (Gigabyte).
- One is in case, in PCIe x16 Slot working fine

For the other two I have 2 expanders, and two slots (PCIe x16 and PCIe x1).
Because the GPUs wont fit inside and it would be overheating both must be on expanders outside case.

I tried all combinations of plugging those cards in those slots but none work as intended.

- Either only card nr.1 worked (0 - Internal, 1 - 1st external (PCIe Expander 0006), 2 - 2nd external (PCIe Expander 0007s))
- Or all showed up but system completly froze. (Only force restart helped)

Each time I swapped, it did one of those.

What can be causing the problem?
Too weak PSU (EVGA 850B, those cards have 300W TDP Each), or
Cable, expanders, or something else?

Well, seems you know that already, I bet you'd do some troubleshooting and tests, replaced higher PSU rating, and replace risers?

post your results, we have to do basics, then lets see on the higher levels.

[Marekkon5]

get some risers
connect all gpus to risers
switch x1 and x16 lane speed to gen1 in bios

Tried, except for the risers part.
Found out that's PSU problem.
Thanks.

[lankyman]

I have had stable mining times and then just really bullshit times where i get blue screens when the miner starts up and scans the GPUs.
A real fking pain.
I have re-installed and taken out cards and then re-seated the cards and re-installed drivers i mean really this is ridiculous.

I notice in my GPU-Z the one card of the 2 or 3 whichever , it always shows autodetect  in the memory type,  and it should be samsung.
what causes this crap