3x mining rig rx570 rocm problem

Hi guys .

So long story short.
I bought 3 mining rigs

3 similar rigs
g4400
Asus prime z and h 270
4gb
6x AMD RX570

So i spend 2 days trying various install of ubuntu 16.04 and 18.04
i finally got rocm working but it only see one card.

After posting on their git , they seems to blame that  is due to the lack of pcie lane on the cpu side , and the mb not providing pcie gen3.
my cpu on ark
PCI Express Configurations ‡ Up to 1x16, 2x8, 1x8+2x4
Max # of PCI Express Lanes 16

my mb z270
1 x PCI Express 3.0/2.0 x16 slot (at x16 mode)
1 x PCI Express 3.0/2.0 x16 slot (max. at x4 mode, compatible with PCIe x1 and
x4 devices)
4 x PCI Express 3.0/2.0 x1 slots

from what i understand rocm , what the pcie gen3 direclty into the cpu not in trough plx bridge type...

My plan was to put those rigs in a octopulis cluster

Is it still possible to have hashcat recognized the hard use another driver like amdgpu pro?
Do i have to go with an older version necessary ?
any good amd setup tuto ?

the bios are mod , could it be only that ?, but then why one is recognized

reference post
https://github.com/RadeonOpenCompute/ROCm/issues/589


any help would be greatly appreciated