Help needed - 4 cards Ubuntu - problems

[PDcologne]

HI guys,

my problem has been going on for 4 days now and i am pulling my hair out.

my set-up

sempron 145
4gb ram (i have tried 8 also)
4 asus r280x
2 750w psu connected using an adapter
gigabyte ga-990fxa-ud3 MB

currently on Ubuntu 12.04 i have also tried 13.10

 
all 4 cards where connected using 2x 1x16 risers and 2x 1x16 powered risers, with a lot of trial and error, swapping and replacing etc i got 2 cards to be visable. i actually bought 6 cards as i want to add 2 to an existing rig, so have tried using different cards also.

all 4 cards are getting power as the lights come on and the fans spin.
 
i have tried aticonfig, i have tried installing the drivers many times, i have tried everything i can find on google....

when i connect an extra card and power up the system i get a purple screen hanging. if i disconnect the card and run with two again it boots fine.

i cannot think of anything else, i have followed numerous guides, (cryptobadger, highoncoins - on yt). i have read through hundreds of posts on here and other forums.... and i am officially stuck.

any ideas or any more info needed let me know....

my wife would also be very appreciative, i think she is about to explode if i hide away for much longer trying to fix this!

thanks
Paul

[PDcologne]

update - i half got three cards working with an install of xubuntu - but again it all went pear shaped from there.

the only other thing i can think of is to try windows, which many seem to have had success with.

the only thing left i can think of.

again any help is appreciated, and if any one can get this running im happy to reward you