I tried BAMT, SMOS, NotSMOS and just about every usb-bootable distro I could find, none of them worked with 6gpu's.

Disabling the on-board graphics in my bios, then installing ubuntu without a graphical envorionment did the trick. When enabling a desktop environment during install I could only ever get 5 cards running, please don't ask me why.

After installing ubuntu I installed xdm and xorg, installed the Catalyst drivers and SDK per instructions here, create a rc.d/xinit per the instructions here and bob's your uncle.

I have no idea why manually installing and doing everything would work different than using bamt/whatever, but hey, it works.

When I just started I tried Windows 8.1 for a while, but that would only hold out for a couple of hours and then suddenly no longer recognise the 6th card. Also, Windows 8.1 is for tablets, screw text that's 150% too big and that silly tile stuff.

It's been running a couple of days no at a steady 5MH/s with none of the problems I had with Windows or BAMT.