Low Hashrate Problem

[MinerC1]

I built a new rig.

Gigabyte Z270p-D3 Mobo
Currently had 4x MSI RX 580 Armor 8G OC GPU's installed.
Powered Risers


I flashed and tweaked each GPU individually and got them each to a stable 30 MH/s.  But once I powered the system with all 4 GPU's installed my hashrate dropped to around 19 MH/s each.  Using the blockchain AMD drivers, mining with claymore.

Modded Bios (only edited the 2000 strap)
Core Voltage 950
Core Clock 1135
Memory Clock 2200

MSI Afterburner also will read all 0's for the cards when multiple are connected but works fine when only one is connected.  Im stumped here, can anyone help me out?

[Plant Power]

Can you mine on just one card while all are connected to see what that hashrate is?

[MinerC1]

I'll try that later today when I get home and let you know the results.

[0xcosmos]

did you enable 4g decoding in the bios?
did you change the pcie lane speed to gen1?
did you increased the virtual mem to 16gb?

[MinerC1]

did you enable 4g decoding in the bios?
did you change the pcie lane speed to gen1?
did you increased the virtual mem to 16gb?

Yes all of the above has been done.

[patofet]

I have like 24 RX 580 8Gb, and each card give me diferent MH/s like, minimum 18MH/s and maximum 28MH/s in the same conditions and the same that your conditions. I'll stay tuned here 

[yhhy]

How big is your PSU?

[AS10]

What is your PSU?

[Daniel0303]

Try Realtime priority in task manager for the miner it works for me on 3 of my rigs

[blue1984]

i have the same problem on linux