11 x GTX 970 System

[kiara]

u dont need SLI for cracking hashes with hashcat.

u dont need more than x4 to crack hashes, the problem that can occurred when using x1 for example is loading big word-list, their will be a bottleneck through the pci lanes.

[jodler303]

I checked my system (1cpu xeon, 2 x gtx1080),
I took the card1 x16 slot and second card is x8 slot then check the benhmark same speed ~417kh ~414kh.
I took the card1 x16 slot and second card is x16 slot then check the benhmark same speed ~417kh ~414kh.

No surprises here.

... i'm getting the same speed for WPA/WPA2 with multiple gtx 980, titan x and gtx 1080 even on a consumer i3 (!) mainboard, it's powering 5 GPUs on pcie x1 each (i can only use x1 because of pci-e risers). The figures are indeed identical for slow hashes like WPA.  

But there may be a huge difference for faster hash algorithms when using dictionaries, so you also have to compare the figures for fast hash-algorithms. The reason is simple:

The faster the hash algorithm, the more passwords per second hashcat has to pump over the pci-e bus to the GPUs (for dictionary based stuff). Therefore the difference between x1 vs. x4 vs x16 will be higher, the faster the hash-algorithm is (if not enough password candidates can be calculated on gpu) - while there is less or possibly no measurable difference for slow hash algorithms.

[atom]

Right, that's why you add rules to mitigate that effect. There should be no difference between and x1 and x16, even on MD5, if you have enough rules added.

[yamahoto]

That seem perfect, but I'd go with 8x 980 for Low Power + Same Performance.

Myself, personally, I have 2 rigs. 
An Nvidia 6x750ti
an AMD 6x280x

I prefer the Nvidia one it runs as silent as my laptop!
The other runs as an airplane and it's the most silent AMD you can get.

[BigDidge]

I'm building my first GPU node here consisting of:

PSU: 2x850w 42Amp [undecided on model and price]
Motherbaord: ASROCK H81 Pro (LGA1150 socket, 1x16 PCIE, 5x1 PCIE) [£45 GBP ebay]
CPU: G1840 celeron dualcore 2.8Ghz (stock intel heatsink/fan) [£28.55 GBP ebay]
RAM: DDR3 8GB (2x4GB) [£30 GBP ebay]
GPU: 6x nVidia GTX570 [£50 GBP each]

Additional components:
Dual-PSU adapter, [£5 GBP ebay]
1x x16>x16 PCIE Riser (non-powered) [£3 GBP ebay],
5x x1>x16PCIE Riser (non-powered) [£5 GBP each, ebay],
2x 3pin 240v PSU kettle lead.

it wont just be for cracking hashes, it'll also be apart of testing prior to upgrading as an additional compute node within my already forming beowulf cluster which also acts as a renderfarm for my engineering using blender and what not so really this node if running at a good rate will be the basis for another four exact nodes all using GTX 10 series cards in the future (waiting for a price drop)..

Nice rig you have designed, would be nice to hear of some updates and what not in the future

[xkeyscore]

Will it run six GPUs? I thought there was a limit based on the amount of memory available to the bios to manage the GPUs. The number I think I read was like 500kb/GPU.

Just because there maybe six PCIe slots, it doesnt mean you can run six GPUs. You might want to check that out.