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Im thinking to build one of these but i dont know which motherboard and processor would be optimal to use.
Do all motherboards with 4 16x pci-e slots support this and is this even possible or is 3x 7970 maximum?
What psu would i need for this?

thanks

Im not sure about motherboards, but you would need a very large psu, prob 1200+, maybe 2. And you would probably need pcie x16 extenders to keep the heat down (because the cards would be right beside each other).

https://bitcointalk.org/index.php?topic=57410.0

4 should work for mining. I've seen 4 done in crossfire but they were right beside each other without any room for airflow. Going by the power draws here, 4x7970 should take about 800-900 watts. Show you should have at very least 1200, but if you are going to overclock probably go with a larger one like a 1500. I can't comment on that brand though. I would go with expanders and suspend the cards with at least 3/4 of an inch between them. But thats just me.

Edit: http://www.youtube.com/watch?v=685-rXNR7o4

Video showing system with 4 7970s in crossfire and full specs.

Saw that thread with 3x 7970 used, thats why i asked if 4 are possible for mining :)

Also saw that youtube vid, but there are 4 cards put near each other and also motherboard and proc used are too costly for mining purposes.. I need "cheap" motherboard where i can put "shit" proc to do the job :P

If you can use 4 in crossfire I dont see any reason why you can mine on 4 of them.

Hardware wise:

This one has 2 pcie x16 and and 3 pcie x1

http://www.newegg.com/Product/Product.aspx?Item=N82E16813128519

This one has 4 pcie x16 slots and would only need one extender but I would reccomend 4.

http://www.newegg.com/Product/Product.aspx?Item=N82E16813128514

If these are too expensive you could always looking in the sales section of the board here for a used motherboard.

Edit: This is a cheap/shit proc that MAY work, Its been a long time since I've looked at processors.

http://www.newegg.com/Product/Product.aspx?Item=N82E16819103888

PCI-e extenders can be found @ http://cablesaurus.com/

For that mobo...

Expansion / Connectivity
Slots
- 2 x PCI Express 2.0 x16 slots (Single at x16 or dual at x8/x8 mode)
- 2 x PCI Express 2.0 x1 slots

2 + 2 = 4

http://cablesaurus.com/index.php?main_page=product_info&products_id=10

Problem solved ;)

haha :D :D

So there is 0 degradation of performance of any kind with doing this? :)

Also do you have a suggestion for ""cheap" motherboard where i can put "shit" proc" that differs from the mobo suggested by dizzy1?:P

tnx

No mining performance degradation (that I know of). But gaming on x1 could be degraded. To my knowledge any board with 4 pcie slots, no matter what the speed can host 4 video cards.

I'd love to have a quad 7970 system for gaming, but for mining you'd be better off with 5970s as they're over 1 MH/watt more efficient.

That is true atm. I would wait to see some optimized miners for the 7000 series before definitivly saying that.

Well 5970's are hard to get and also u take a risk of it being used.. And i can get 7970's quite cheap..
How do you guys think 7990 will perform? Im asking myself if i wait for it..

Also can anyone suggest me motherboard from asus or asrock because i can get these cheaper?

See one news,one pci can add 7 cards.

link?

At what cost?  More than an entire computer system?

external PCIe and PCIe switches have been around for a long time they just don't make economic sense.

Define cheap?!?

Doesnt sound very cost effective at all. 6950's can be had for $200 each which is cheaper and cranks out more hashes with 2.

Yeah, that is an issue, gotta maximize, you're computer as a whole.

I suppose using riser can help to add more cards card via a mounting bracket for room ( I would assume risers would help increase airflow in most open board configs )

but I guess the logic I almost missed was .. 4 x 6950 vs 4 79xx,

you get 1316 mh/s with 4x 6950
you get 2400 mh/s with 4x 7970  ( I took a 650 single card and reduced performance to 600 just for heat and w/e argument sake)

But you still probably get the best performance with a 5970, might be harder to find, but if you got 400 bucks cad, or usd you can get atleast 1 a week via craigslist / kajiji not so much so on ebay though.

What can we do except this on this forum.. where restrictions are important than users!