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I had been going 6 x 7970, but everyone says the 7950 is best.

Is 620 Kh/s easily doable on most 7950's?  I get 670-720 Kh/s on my 7970's

What power supply is needed for 6 7950's?  I'll have 3 on powered risers and 3 getting power off the board.

I would say rather, 600Kh/s is "pretty easily" doable.  Depends on the card, V lock etc for getting above that.  Many can hit 620 if tweaked right though;  may take a bit of playing to find that on yours. 
 
For power and depending on your final OC, your probably looking around 180-200w per card. 

How do you have 6 7970s running? What driver? What SDK? What OS? I have problems getting more than 4 on win7 x64 using driver 12.8 or higher. I'm barely able to get 5 going with 12.6

Thanks for the feedback... so 3.6 Mh/s per 6 card rig should be done easily on a 1500 Watt or more Power supply? 

Can someone running 6 x 7950 pipe in on the power supply they use and watts at the wall?

I'll drop you a PM to keep this post on my topic :P

Ye, 1500w would allow you 300w of room for your mobo, ram, hdd, etc.  You may look for a 1600 though as you'll probably get a slightly higher efficiency of conversion.  This may differ with PSU mfg., but you can tell from reviews and such.

For connecting to the wall.  1500w is the maximum that any electrical device can be approved for 130v 60hz.  Pretty much all electric heaters are 1500w, so as long as your in a situation that is safe for an electrical heater (e.g. up to code). no worries.

im also wondering how to run 6  ::)

Depends what country in OZ we run 240 volt (thank u jesus )

So we happily can run 2400 watts per plug :P

Quit braggin :P

Here is a link to the current low spec unit that I get 650+ pushed and 630+ easy peasy lemon squeezy

http://www.pcmeal.com.au/computer-hardware/video-cards/sapphire-ati-hd-7950-oc-edition-with-boost-3gb-384-bit-gddr5-850mhz-boost-925mhz-5000mhz-2-x-dvi-hdmi-dp-dx11-1-fan.html

Also I think u should start a thread with photos and as much detail as u can muster for your 6 card rig :D

Its like you have captured a unicorn and we all want to see it :D

Th comunity would be eternally grateful btc and ltc

Lol.... I didnt figure 6 card rig was that tough or rare, but after finally doing it, I can see why.  I'll try and get some pics/etc together and post in this thread when its done.  My freet time is very variable at this point, so dont hold your breath but hopefully I can get something together this weekend.

We all know it exists but to get documeneted proof and with current tech i.e 990fxa  mobo and 7xxx series GPU's this is golden  8)

There is nothing "easy" about running 6-card rigs, especially 79xx cards. From risers to PSU(s), motherboard choice, power consumption, THERMALS, everything is rather "hard" so yes, I'd like pics and details too. :)

If you are running 6 cards can you use all unpowered risers?  Or do you need powered risers?  What happens if unpowered risers are used?

unpowered if you run like me and undervolt the cards, if you run them at stock or OC then go for powered ones.

Depends on the motherboard.  Some have a supplemental port (4-pin Molex, 6-pin PCIe, SATA) when additional slots are filled.  If yours doesn't have this option and you try adding 4+ cards, you run the risk of pulling too much current and frying your 24-pin cable.

Even then I would go for powered ones unless you have good quality riser cables. Perfectly possible to burn the riser cable itself with cards that are pulling upwards of 250w unless they are of good quality. If I can find one of my shit ones ill post a pic of the difference in thickness of the individual cables of a good vs bad riser cable.

GPU will never (or is not allowed to) pull more than 75W from the PCIe bus. That is the limitation of PCIe standard, all the extra power is being pulled from those PCIe 6/8pin connectors.
Riser thickness or quality doesn't really matter in this. The thicker one is probably just having more insulation around the actual wire inside the cable.

7 Series cards seem to have some software issue in Windows if you go +5 GPUs. You can do 5 with 12.6 catalyst, but after that not sure if it's even doable. I went for 7970s since I can pack 5 of them in one rig and that runs nicely with a 1500W PSU while having plenty of room for OC. 6x7950 would have been interesting option too, but maybe not for a Windows machine.