4x Sapphire Nitro+ RX 570 4GB
ASUS P5Q Pro Motherboard
Windows 7 64-Bit
Every time I add the 4th GPU my hashrates drop from 24 to 4 MH/s on GPU0, regardless of which PCI-E slot I add it to. I've tried everything from swapping slots, risers, and ensuring my BIOS drivers are up to date (mind you it's an old mobo; 2009).
3 GPU's run fine. With the 4th GPU in, 3/4 run normal but GPU0 always dogs to 4 Mh/s. Any idea what's going on here?