I have the GPUs at 70o and adjust the fan automatically with a control script

Max acceptable fan speed for me is about 70%; more than that level it is very noisy and I can't stand it. Besides, I also afraid that high speed could kill the fans quickly

Ambient temp is around 25oC at night to 33oC noon.

Well, I do not have any concern about the Molex connector but the motherboard itself

Do you think the traces in your board can support all that current? And the power comes from the molex connector will be routed to the PCI-E slots with big enough traces or the motherboard designers decided to route it to the CPU? Or half and half? Or anything else?

Simply said, we do not have much info how a particular motherboard was designed. So a safe bet is not to put too much current on it.

Down time is expensive

2 cards -> no problem

3 -> I don't know

4 ->  Some have problem with the ATX power connector, burnt and melted. Must use pci-e extender with molex power connector

Or you can use expensive main boards which have additional power connector (Molex or EPS); usually gaming boards. But I think they're not worth

Thanks D&T. I have to start filling up my piggy bank then.

And how much will it cost?

Double the price of 7970? Ouch!

For me it is because FPGA route will not give me any fun.

1. I know a little bit about FPGA, but it is not enough for actively engaging a FPGA mining project. So, with FPGA route, basically I just bought some black boxes and then connect power supply to the black boxes and then run the miners. Period. Do you think it is fun?

2. Upfront cost is too high. I just don't have such a big deal of money to burn.

3. With GPU route I can play with them for many hours! I build the frame (metalwork is my hobby), setup the rig, playing around with the settings, overclock, underclock, write control scripts...Countless activities.

4. It is not risky, I can sell my GPU at a good price

I had the same idea and found this. Quite cheap, 100 bucks for 2.1kw

https://www.google.com/search?q=Dell+NC003+power+supply&hl=en&safe=off&client=firefox-a&hs=I91&rls=org.mozilla:en-US:official&prmd=imvns&source=univ&tbm=shop&tbo=u&sa=X&ei=_wYsT4KxGtHJmAWqyInqDw&ved=0CEYQrQQ&biw=1366&bih=675

It is an used dell blade server PSU, rated 2100w with 12 volt 175A max. I don't know how many rails it has.



Also not sure about its efficiency. And how to start this little monster is the problem. It has some kind of control board for hot plugging function, not just a dumb PSU

Agree

FPGA is boring, unless you know VHDL or something like that and would like to do some experiments.

And it is quite risky because it is hard to resell that FPGA board. I can sell my graphic cards to the gamers at any time.

With VGA it is more fun. I spent a lot of time writing automatic control script for my cards. It can't be compared with cgminer or other "professional scripts" but to me it is the best

1. PSU: 80plus PSU, trusted brands only

2. CPU: Cheapest, lowest power consumption cpu you can get

3. Motherboard: Cheap one with 4 pci-e slots at minimum, 3 pci-e 1x and 1 pci-e 16.

That's a big number!

I'm using 1x extenders. No problem so far.

I think 1x pci-e extenders are good because they don't restrict airflow from my box fan; cool air can goes through the space between the motherboard and cards. I do not plug any card in the motherboard directly because doing so makes my cards hotter than using extenders

And when you run 2 power supplies on a single rig, you must use extenders that have molex power plugs (quite easy to mod it)

How long have you been running with that 60%?

Don't count on that

I have some 6950 Asus DCII 1G, non-reference cards. 02 cards are unlockable, others are not.

It is up to your luck 

6970 is just too expensive compared with 6950.

But I think 7950 is the way to go in the long run

Hi,

Just curious to know what fan speed you guys are using? I just don't want to let the fans die too soon. My card is Asus DCII, running at 70oC at 50-60% fan.

Is 50-60% fan speed 24/7  OK for the fans? They are sleeve, not ball bearing fans.