7950 or 7970 for mining rig

[thedonvon]

Building an open case mining rig.  my buddy (Xwebnetwork) will be building one as well.  We are undecided about going with 7950 or 7970...what do you think.  Here is my rig

Mobo - http://www.newegg.com/Product/Product.aspx?Item=N82E16813130643
CPU - http://www.newegg.com/Product/Product.aspx?Item=N82E16819116889
PSU - http://www.newegg.com/Product/Product.aspx?Item=N82E16817103089
Memory - http://www.newegg.com/Product/Product.aspx?Item=N82E16820145345
4x 7970 - http://www.newegg.com/Product/Product.aspx?Item=N82E16814150586
or
4x 7950 - http://www.newegg.com/Product/Product.aspx?Item=N82E16814202026

not really sure about GPU selection...I have been trying to research but am seeing mixed reviews on hash rates.  I do not have my heart set on the GPUs listed above they are just the ones which seem to have the best price currently on newegg.

Also i want to get powered risers right?

Thanks for all the help!!

[ruecanonrails]

I'd go for the 7970's personally as they have more use outside of mining and a better resale value when the time comes.

[middlemarkal]

that mobo only has 3 pcie*16 slots so you need at least 1 riser 1 to 16  

If you have the money go for 7970, but why not 5 * 7950 if you use riser ?

also sparkle is not the best kind, go to jonnyguru and check his evaluation of big PS.

[thedonvon]

yes i am going to be using 3 x16 to x16 risers and 1 x1 to x16.

I want to start with 4 GPU and will probably end up expanding this rig down the road when i recoup some of my investment.  I should be able to run a total of 7 with this mobo so all i need to do is add another PSU because i dont think any PSU could handle 7 7979s lol

any suggestion on PSU?  i thought that would be a good one being it is 80 plus gold certified

[HackneyB]

have you thought about the fact that these cards consume 200-300W and that to have 5 of them your PSU may need to be monstrous?

Also seems this only makes sense now if you want o resell or use those cards elsewhere .. if buying only for Bitcoins some cheaper cards may make more sense based on how much processing power you get per card cost. 

7970 - 600MHash/s and $400
7770 - 200MHash/s and $100

[thedonvon]

have you thought about the fact that these cards consume 200-300W and that to have 5 of them your PSU may need to be monstrous?

Also seems this only makes sense now if you want o resell or use those cards elsewhere .. if buying only for Bitcoins some cheaper cards may make more sense based on how much processing power you get per card cost. 

7970 - 600MHash/s and $400
7770 - 200MHash/s and $100

7970 consume 270W and 7950 consume 190W.  I am only going to have 4 GPU to start and when i add more down the road i plan to add a second PSU.

You would need way to many 7770 to make it worth while.

[Xenotron]

7950 does 550-600 Mh/s, price ~ 300-330$
7970 does 600-700 Mh/s, price ~ 400-450$

Does it make sense to buy 7970? Can't see any.
The only exception is if you are not limited by power consumption (free electricity) and can build effective cooling system, but you are limited by space, so it's better for you to build 1 system with 4 7970 than 2 systems with 3 7950 each. As example.

The best choice from price/Mhs perspective is smth like used 5850 cards, IMO. Price is ~ 100 USD while they can do 250-300 MH/s. But power consumption and temperature are insane...