WORKS
Motherboard Brand: Biostar
Motherboard Model & PCIe Slots: A870U3 (2x16, 2x1)
Power Supply Brand & Model: Corsair TX850 (Pulling ~615W at the wall)
Number & Model GPUs: 4x Sapphire 5830 Xtreme (Overclocked & undervolted)
Extender Cables w/Molex Power?: No
Motherboard automatically unlocks 2nd core of Sempron 140.
I'm trying almost exactly the same configuration, except with 5850's and it's not stable. Are you using 16x->16x extenders for the two 16x slots? Have you noticed any stability issues?
I have two 16x->16x and two 1x->16x extenders. No pin-mod for the 1x PCI-e slots. Rock solid stability. Using LinuxCoin booted from 4GB USB, running headless.