I have a Biostar A870 that is rock solid with 2 GPUs, but flaky with 3, and with 4 is very unstable. There is plenty of PSU power (1000W with max power draw at socket <800W with 4 GPU on full load).
Is there a board that is working well for others with 4 GPUs without the need for the extender with the molex connector (way too expensive)?
I would highly recommend the asrock board linked below. It's been rock solid (no pun indented).http://www.newegg.com/Product/Product.aspx?Item=N82E16813157262