I use X16 risers in all three X16 slots and I run 5 GPUs on this board. After building a few rigs for friends and my own few rigs I have come to the conclusion that each mobo / GPU is different and you just gotta see what it is gonna take to make your setup work.
One mobo want the X1 presence pins shorted one doesnt. One will run with all 5 cards on a 1.09V BIOS one wont, one wants powered risers in the X1 slots one doesnt care.
Just gotta figure it out. Easiest way is to pay attention and figure out what you have done already. Just going at it switching things around will get you no where and aggravate you. If you want to check the powered risers part then check each card remembering which ones you have done. Write it down so your not trying the same thing over and over again.
You have to figure out which combination of powered / not powered risers, presence pins, BIOSs, etc will work.
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I agree with you may I can add some of mine.
I start only with one card connected via a 16 to 16 riser.(I ALWAYS with a 16 x16 riser for this first card in the primary pcie X16 slot).
Risers 16 x16 unpowered and x1 risers powered and I to experienced that some times the power molec of certain risers should not be connected.
I use windows 8 as OS.
Always start with a clean OS windows 8.
Than load the latest catalyst drivers for your GPU.
Than start installing the second GPU with the 1x riser , If this one is reconised, than restart the system and install the third gpu withe 1x riser. etc.
This goes on until you reached the last 5th card. Maybe this is not always necessary but for me it works without any stress
Do'nt change the ranking of the cards, you cannot change the risers to put them in an other slot.
If the system will not instal the card during process, please start up en retry this several times until its see in windows.
If the fan speed suddenly goes up during install just restart the system. Do not change anything.
Do not change the installed risers and the cards attached to them. In order to make this easy just number the cards with a label attached on them.
If all finally works than make a back up an image on the disk so you can always recover. Make a note or photo of the cards with their exact place on the board. Never change that. If it is changed however start the whole procedure again if the system does start anymore.
In my experience every card is unique and need via the pcie slot a fixed installed position.
It is possible to connect a six card to the system with the mobo Asrock H81 pro BTC ( a much easier board to install) but in that case the procedure of the last GPU (6th) installment differs a bit.
I have used also gigabyte GA 277X-UD3H mobo.
If you ever use other boards , please start with the chip-set info of maximum lanes, than use the info of the mobo architecture of the slots and maximum lanes they can handle.
Start counting the slots to be use starting from the lowest (x1 or x4) than decide which slots above need to be used. In that case be certain that slots are not blocked if a slot with a higher number of lanes is used. Some times a 16x slot needs shorting to recognize the GPU.
Than start in the same way as described.
If the system finally does not work please start all over with a clean windows 8 newly installed, do not continue with the old windows 8 OS already installed.
My advice: Work with a fixed scheme and be patience.
