I've got two of the exact same motherboard you have, and I'm running six cards each as well. Using Ubuntu 12.04.2 LTS. I can't really say anything about Windows vs Linux, I've only been mining in Linux.
Yes, you do need a presence short on the 3rd PCIe x1. I've got all my cards on x1 to x16 risers (even on x16 slots) and had to do the presence short on that last x1 slot and the x16 slot just under it.
There aren't any additional power lines on the longer PCIe slots, x16 won't have any more than x1 does. Take a look: http://en.wikipedia.org/wiki/PCI_Express#Pinout - all of the power pins are on the little section before the notch.
On my boards, I use three unmodified and three powered risers. With my powered ones though, I sever the +12V lines going to the motherboard so that it only pulls power from the molex. I actually have those powered risers powered off the second power supply.
If you don't sever the lines, you have to plug those molexes into the same power supply that's powering the motherboard.
1600 watts should be enough, I measured one of my rigs with a Kill-A-Watt at about 1500 watts with all six cards running (before playing with voltage). I actually over-spec my power supplies, each rig has two in the 900-1000 watt range.
There's a mining rig in your bathroom?
Now for the issue of PCIe slots, all three of my 16x slots handle non powered and powered extenders fine. my 1x slots one and two are good, but the third one I think might need a presence short, it was being picky. As far as powered extenders go, I was planning to do something like all the 16x powered(three) and 1x (three) non powered. This should be ok I think, or do pcie 1x pull less power through the board and would benefit more from a powered extender? And or should I just power extend all 6 of them?
Yes, you do need a presence short on the 3rd PCIe x1. I've got all my cards on x1 to x16 risers (even on x16 slots) and had to do the presence short on that last x1 slot and the x16 slot just under it.
There aren't any additional power lines on the longer PCIe slots, x16 won't have any more than x1 does. Take a look: http://en.wikipedia.org/wiki/PCI_Express#Pinout - all of the power pins are on the little section before the notch.
On my boards, I use three unmodified and three powered risers. With my powered ones though, I sever the +12V lines going to the motherboard so that it only pulls power from the molex. I actually have those powered risers powered off the second power supply.
If you don't sever the lines, you have to plug those molexes into the same power supply that's powering the motherboard.
Now do you think a 1600w 80 plus gold psu the Lepa one, that should be able to handle x6 cards just fine.
1600 watts should be enough, I measured one of my rigs with a Kill-A-Watt at about 1500 watts with all six cards running (before playing with voltage). I actually over-spec my power supplies, each rig has two in the 900-1000 watt range.
-my gf wrote this while staring at my rig sitting on the toilet
There's a mining rig in your bathroom?
You have the same motherboards!!! YES!!!! With 6 running?! *hallelujah* That literally just relieved me so much, because I really didn't want to go through the hassle of having to order a different Mobo/CPU setup.
Ok, presence shorts on the thrid x1 slot assuming your counting the northbound (coming from cpu moving down the board) one as #1 then pcix16 then pcix1 # 2 and pcix1 # 3 and pcix16 pci 16 end of board
So I need to presence short pcix1 #3 and pcix16 just under it? Got it. Could you send me pictures of your presence short? I've seen pics on line for a 1x slot, but not of a 16x, or if you could link me to a good pic/diagram.
I have powered x16 to x16 extenders, I have powered x1 to x16 as well, but they were done incorrectly and don't provide the extra 12v I think... None the less i have the 16 to 16 which I know were perfectly, and since I'm using one PSU and its the same one for the mobo I don't need to sever any of the lines.
Yeah I have these MSI cards and they undervolt just fine in windows so hopefully it won't be much of an issue in Ubuntu, any advantages to Ubuntu or Xubuntu?
Any chance you mind emailing or IMing me or some kind of instant communication and we can discuss a little more?
Oh and in regards to the song my gf wrote lol, we live in these new apartments for college students and our walk in closet is actually through our bathroom, so you walk into the bathroom and then theres another door to the closet which is directly in front of the toliet and often open, and in there on the top shelf under an AC vent are all my rigs Lol so she had a clear view of them
Sorry for the confusion, if you're using x16 to x16 risers, you shouldn't need to do the presence short for the x16 slot like I did. I had to do it because I had the graphics card there on a riser like this one: http://www.amazon.com/Micro-SATA-Cables-PCI-E-Riser/dp/B005G4SADY/ref=sr_1_1?ie=UTF8&qid=1370553268&sr=8-1
So it was only connected as x1 even though it's plugged into an x16 slot.
And yes, the farthest x1 slot from the CPU is the one that needs the short. I actually just peeled the presence lines from the risers, clipped and soldered them together because I didn't have any wire that fit very well.
Undervolting is harder in Linux, or so I've heard. If cgminer can't do it you're pretty much screwed...
The real advantages of Linux are 1) free and 2) can be installed to a flash drive.
Right ok so then I just followed this diagram
http://blog.zorinaq.com/images/pcie-short-schematic.png
and did that to the third pcie 1x slot, thats the only thing thats need to be presence shorted
Yeah windows just craps out in so many departments though, remote desktop client wouldn't work, updates forever and ever, system instability, I'll give both a go and see what happens. Which drivers did you use in Ubuntu?
And what BIOS settings did you tweak? Also, are you using dummy plugs? actual plugs? no plugs?
Thanks