Today if you have the cash (these things can get stupidly expensive), I don't think you won't find a PSU capable enough for 13 GPUs at once.
However I've seen some guy built a rig with 2 PSUs into the same system, a cheaper and more reasonable solution I would say. This mostly saves you the cost of an additional Motherboard + CPU + RAM and also saves you the power costs for the additional system.
Today if you have the cash (these things can get stupidly expensive), I don't think you won't find a PSU capable enough for 13 GPUs at once.
However I've seen some guy built a rig with 2 PSUs into the same system, a cheaper and more reasonable solution I would say. This mostly saves you the cost of an additional Motherboard + CPU + RAM and also saves you the power costs for the additional system.
Let me see if I can find one... there, find it in your own language if you please :)
PS: sorry for the late reply, I was away for quite some time :)