just a heads up for everyone
ive flashed 10 gigabyte GA-Z170-Gaming K3 to latest bios F20
9 out 10 work flawlessly with 6 cards no need for changing any settings in bios
they work plug and play now
been stable for 2-3 days now
for anyone with the following board
ASROCK Fatal1ty Z170 Gaming K6
using BIOS 2.8
can run 5 cards by doing the following in the bios
go to advanced mode
and chipset settings
Change PCIE to gen1 on both options
change max TOLUD which is the next option down from the above to 2.5GB
this makes 5 cards work
I have not got round to flashing the bios yet to reassess if can do 6 cards