6-8gpu rig need advice?

[unforgiven]

Hi everyone
i'm getting ready to build a rig and need some help over here.
it's going to be a 6-8gpu rig with 2 psus and proper cooling.

so what i don't worry about is its cooling, power supplying and the graphic cards as they are already bought and i'm just gonna use them so please no comment on this semi-setup which i'm stuck with.

i also have:
1 powered usb3 x1-x16 riser (CAN'T afford any soon enough)
2 x1-x16 non-powered risers (can afford more)
6 x16-x16 ribbon risers (can afford more)

I need your help to figure out what is the proper motherboard and processor to take at least 6 graphic cards?
considering it would be better using the most from 16 links on each PCI-E (for dictionary).

mobo models which i think might be good:

Gigabyte GA-990FXA-UD7 (not availible aroud here)
MSI 990FXA-GD80 (not availible aroud here)
ASRockH81 Pro BTC (not availible aroud here)
ASUS ROG STRIX Z270F GAMING
*ASUS X99-E WS

The last one is the one i can find/buy easily although it's a little expensive(especially with a 2011 core i7 cpu which would be useless for me as it's the gpus doing all the process - still not sure about this)

So i'm going to ask for a MOBO and suitable CPU and RAM of course.
i have no idea on the amount of RAM either.
could anyone advise me on these please?

[gscotch]

Hi
Probably it's too late but anyway

mobo asus z-270-p with
2x M2
2xPciex16
4xPCIE1

you can setup 8 GPU rig using riser M2 to PCIE4x and risers PCIE1x to 16x

4GB RAM DDR4 it is enough

CPU celeron g3900

[winxp5421]

Just a word of caution I really hate the 16x->16x ribbon style risers ( or ribbon style in general ) I have personally blown the traces right off of them/melted the wires clean off (powered or non-powered both end up the same). Invest in the USB style risers not only do you get more length they are far more reliable.


edit: Jesus dude, resurrecting a 6-month-old post?!