whats the advantage of these besides the extra length?
Im planning on trying to run 5 290's per board and have been reading about problems trying to get windows to see all the cards and people having to short certain pins in the risers to get it to work. Do these take care of all those issues? Do these cables meet the industry standard for load tolerance and insulation etc.. all it takes is one bad cable for the whole operation to go up in smoke?
side question to anyone: could you recommend a 1350w psu gold with 4 pcie 6 pin and 4 pcie 8 pin connectors? ( will a 1350w be enough for 4 R9 290's (non x) Tri X (sapphire) cards (and nothing else)? I was told they take ~275w each- have I enough headroom?
You don't actually do anything to the riser itself, the pin shortening process is with the pci slot on the motherboard with a cat5 or 6 cable. See
https://bitcointalk.org/index.php?topic=36061.0 for more info on this.. As for the psu you might be better off splitting the load between two seperate PSUs and use an adapter from
http://www.add2psu.com it's probably just the same cost if not cheaper this way and its less stress on the PSU.