8 gpu target ASUS Z270 / MSI Z170A GAMING PRO CARBON

Hi i'm looking for build a rig for Eth, i wanna use 8 gpus i need some info between this mobo:

MSI Z170A GAMING PRO CARBON
Asus Z270 A

Both MB have 7 pcie and 1 M2 connection than we can add 8 gpu, somebody just did it?
Cause i know on MSI require a special firmware not provider by MSI (where i can found it ?) for 8 th gpu and about Asus i dont' have idea if need something special

Thanks for any info.