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[Evil-Knievel]

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[Collectrix]

I recommend you return those 290x, the performance/watt are relatively poor and the cards are typically not as powerful as the press version unveiled earlier.  Here's a new story about that: http://www.tgdaily.com/hardware-features/82287-retail-radeon-chips-still-go-slower-than-review-versions

The 7950 and 280x are still probably the best value/watt.

[CoinBuzz]

A question:

i dont think 850watt PSU is enough for 4 GPU, since each GPU is taking around 300watt.

How do u want to manage it ?

[darksoft]

Why only 2 cards per motherboard? Seems extremely wasteful

[vrm86]

Can't see any risers for cards, or just not mentioned?

[shtako]

Seems like a poor plan. 5 rigs with 4x 7950s would give you slightly more hashpower at a much lower price.

[cryptomining]

cool project, keep us informed, best of luck!

[mattle74]

Seems like a poor plan. 5 rigs with 4x 7950s would give you slightly more hashpower at a much lower price.

Not really easy to find 7950's for sale anymore. Have you seen the prices on eBay? Not saying the OP is making the best choice but I don't think your critique is fair.

[shtako]

Seems like a poor plan. 5 rigs with 4x 7950s would give you slightly more hashpower at a much lower price.

Not really easy to find 7950's for sale anymore. Have you seen the prices on eBay? Not saying the OP is making the best choice but I don't think your critique is fair.

You are right. Sorry, didn't know they were of the market.

[JohnDorien]

Seems like a poor plan. 5 rigs with 4x 7950s would give you slightly more hashpower at a much lower price.

Not really easy to find 7950's for sale anymore. Have you seen the prices on eBay? Not saying the OP is making the best choice but I don't think your critique is fair.

You are right. Sorry, didn't know they were of the market.

you can get cheap 7970's now..

and OP, why only 2 GPU per Board? total waste imo

[Amph]

a much better system if you don't like raiser(that's why you bought 6 MB right?) would be 4 MB with 2 x 280x each(8 vga in total), 6000kh/s, lower hash rate, but also a very lower investment

[KingGoon]

A question:

i dont think 850watt PSU is enough for 4 GPU, since each GPU is taking around 300watt.

How do u want to manage it ?

second that . 850 wont be enuff 

[rwessels]

Where are you guys getting any AMD cards better than a 78xx?

[fruitcommander]

Seems like a poor plan. 5 rigs with 4x 7950s would give you slightly more hashpower at a much lower price.

Not really easy to find 7950's for sale anymore. Have you seen the prices on eBay? Not saying the OP is making the best choice but I don't think your critique is fair.

You are right. Sorry, didn't know they were of the market.

you can get cheap 7970's now..

and OP, why only 2 GPU per Board? total waste imo

Tell me where I can get cheap 7970's right now. I'll buy every one of them.

[bitpop]

Updates

[skleven]

Cool project.

But i think the 290X is the worst miningcard in the R9 series. In my country, you get 2x 280X for the price of one 290X.
And a 280X hashes around 750kh/s @under 250w(and my 3 vapor-x all run stable at 53-55c). But good luck with the 290x, and i hope you do well.

[C3ALL]

Am I reading this right??  12,000 KH/s  for $15,000

I just built a 2800 KH/s machine for £1100 BGP - or around $1,750.   5 x my setup would be 14,000 KH/s for £5500 or $8,750.

Im using MSI 7990 cards.  Managed to find a deal on these for £350 ($560).  With 2 cards this runs at 1250W.

[jomay]

Am I reading this right??  12,000 KH/s  for $15,000

I just built a 2800 KH/s machine for £1100 BGP - or around $1,750.   5 x my setup would be 14,000 KH/s for £5500 or $8,750.

Im using MSI 7990 cards.  Managed to find a deal on these for £350 ($560).  With 2 cards this runs at 1250W.

*g* sounds strangely familiar to me. The cards were actually 357-360£ on Scan's "today only" page which is more like 580-590$ per card. And that was a one-off, probably never to return deal

Somewhat off topic: how do you keep the cards cool? I can run a single card @stock voltage and speed ok, but even then it gets hot. Two cards go into meltdown, so I am currently undervolting and running them only at ~900MHz. I'm thinking about modding the cards soon (thermal paste, removing some shields to get more air to the card etc.). Oh, and total power draw for my setup is definitely <1KW at the wall - I think I measured 750-800W total.

[verloren]

How do I cool them:

Well I decided to cool them with the simplest method possible: I placed them in front of an open window. Outside air temperature is like 0°C, so the cards can suck in freezing air, and block the warm air back outside.
While this method works fine, its really uncomfortable. I am right now wearing a winter jacket while sitting in front of the computer.

Uhhh, the way your computers are set is so they are pulling air from the room, warming it, and pushing it towards the window.

Maybe you should turn them around? That way the warm air goes back into the room.

Might be noisier, but should be a lot warmer than the way it is right now.

[deamon]

where is the point that this hardware give you the money you invested back?
do you calculated a timeline who is give you a decent income?