I want to run my two rigs with 4x 5850 cards each without any external I/O. Do I NEED at least one monitor to keep them running?
Or do I just need one monitor to boot up?
Or do I even need 8 dummy plugs for each card? Can those be bought or must they be built by myself?
One dummy plug for each graphics cards minus the connected to the monitor.
You did not even try to read Helpful Articles for Newcomers (Please read before asking for support.) did you.
Helpful Articles for Newcomers (Please read before asking for support.)
Can I mix up cards from different labels, like 2 Sapphire, 1 Asus and one XFX?
Yes you can mix up cards.