i'm using gigabyte am2+ and am3 old motherboard just about 25-30usd(not new) in here
it have 5 pcie and i'm using 1 to 3 multiplier so all is 7 gpu
and it's all work fine
,all x4 procesor.
i have asrock btc it just can boot with 7 gpu too,cannot boot if i add 8 gpu,no mather what procesor i put on it.
i have asus rampage black edition too(expensive one),it just support i7 procesor,it has 6 pcie,using 1 to 3 multiplier it can boot 8gpu.
biostar 990fxa am3 it have 4 pcie..i can add 2x 1 to 3
..but it just can boot 7 too,cannot boot if i add 8.
the most i can add gpu is in z170 asus(expensive too),if i'm using celeron it just can boot 7 gpu,if i'm using i7..i can add 2 of 1to3 multiplier and it's working all.
so until now if i build new rig,i just using the gigabyte old one,it's very cheap hahaha
it have 5 pcie and i'm using 1 to 3 multiplier so all is 7 gpu
and it's all work fine

i have asrock btc it just can boot with 7 gpu too,cannot boot if i add 8 gpu,no mather what procesor i put on it.
i have asus rampage black edition too(expensive one),it just support i7 procesor,it has 6 pcie,using 1 to 3 multiplier it can boot 8gpu.
biostar 990fxa am3 it have 4 pcie..i can add 2x 1 to 3

the most i can add gpu is in z170 asus(expensive too),if i'm using celeron it just can boot 7 gpu,if i'm using i7..i can add 2 of 1to3 multiplier and it's working all.
so until now if i build new rig,i just using the gigabyte old one,it's very cheap hahaha

asus rampage black can you mine with 8?
yes i can mine it with 8 with linux
in windows 10 it detect 8 gpu but 1 of them is error 43,i try multi gpu app it's still only work 7 in windows