It depends on how much you can overclock the card while decreasing the voltage to it.
The entire thing is a balancing act.
The more powerful cards you have - the fewer motherboards you require.
There is a big overhead in running more machines with less powerful cards in it.
The best you can do at the moment is 4 * 7970 in one machine - that will give you the most mh/s per watt
This will pull around 1150 watts at the wall and 2.8gh/s
There is a bios memory limitation in installing more than 8 gpus in one machine. a 7970 counts as 2 gpus.
If you try and connect more you the card will show up in device manager with an error against it.
Topic: Best GPU for mhash per electricity usage? (Read 1717 times)
Hd7950s! 7970 use a lot more power, and cost 30% more for 17% improvement in H/s. hd7950s only use around 200w each. Much better long term. I use 7950 in all the rigs I build, unless I have a customer that can't be talked out of using 7970s 
If you're investing in GPU mining, you have to go big or go home at this point. Remember to check out the hardware comparison guide, and see where you get the most MH/$.
Either a 7950 or 7970 would work very well, as long as you buy bulk.
Either a 7950 or 7970 would work very well, as long as you buy bulk.
What makes difficulty go up so much??
People with ASCI miners, and increased awareness of Bitcoin resulting in more people mining. The more hashrate you throw at the network, the more the difficulty increases to compensate.
What makes difficulty go up so much??
At todays prices ... you will make about 7.50 per day with a 7970.
53 days range to pay it off, if the market stays at 105 USD per BTC.
That is not too bad in my opinion. That is including power cost on this calculator I found.
53 days range to pay it off, if the market stays at 105 USD per BTC.
That is not too bad in my opinion. That is including power cost on this calculator I found.
Wrong because of 2 reasons: 1) high chances the BTC per USD rate will drop.
more importantly 2) you didn't calculate in increasing difficulty factor.
Use: http://dev.bitcoinx.com/profit/
even that's not accurate, since in a week or two you already have a diffciulty of 11+ million
At todays prices ... you will make about 7.50 per day with a 7970.
53 days range to pay it off, if the market stays at 105 USD per BTC.
That is not too bad in my opinion. That is including power cost on this calculator I found.
53 days range to pay it off, if the market stays at 105 USD per BTC.
That is not too bad in my opinion. That is including power cost on this calculator I found.
6930 gets speed like that for that cheap?! Interesting.
I still think I am going to roll with 7970s for now. 7990 is too much ... but 400 I can roll with because they will hold their value for a long time like a nice used car!
I see 5850s out there for 180 range still. That is INSANE!
I still think I am going to roll with 7970s for now. 7990 is too much ... but 400 I can roll with because they will hold their value for a long time like a nice used car!
I see 5850s out there for 180 range still. That is INSANE!
Can you guys help over here?:
https://bitcointalksearch.org/topic/what-should-i-but-to-start-mining-180268
https://bitcointalksearch.org/topic/what-should-i-but-to-start-mining-180268
The best card is the one you already own. Spending money on a GPU at this point is a losing proposition for *most*.
EDIT:
Expanding upon that... If you have $400 to spend, spend it on actual BTC. Then you will have ~4 BTC now. A $400 GPU will get you 4 BTC... when??? Diminishing returns every 2 weeks, plus electricity cost. Alternately, you could spend it on an ASIC mining contract, or actual ASIC hardware. Just not GPUs, if you're expecting to make a profit.
EDIT:
Expanding upon that... If you have $400 to spend, spend it on actual BTC. Then you will have ~4 BTC now. A $400 GPU will get you 4 BTC... when??? Diminishing returns every 2 weeks, plus electricity cost. Alternately, you could spend it on an ASIC mining contract, or actual ASIC hardware. Just not GPUs, if you're expecting to make a profit.
I think any AMD 5830 is the best bang for the buck. Its hard to find them for sale anywhere.
whats the Mhash on this card? 
Oh I was comparing 7970 vs 7950.
I currently use 5870's, and they are not easy to find either.
I currently use 5870's, and they are not easy to find either.
true but cost to buy the card is more.
From what I have been reading the 7950 is very efficient.
I think any AMD 5830 is the best bang for the buck. Its hard to find them for sale anywhere.
Obviously 7970 and 7990 are the best ones.
But I personally like very cheap 6930, that could easily get 320, or even 350 Mh/s and cost 80-100$
But I personally like very cheap 6930, that could easily get 320, or even 350 Mh/s and cost 80-100$
I just figure that I should get a 7970 or 7990 because if asic really does come out I can always sell the 7970 card on eBay or something probably for really close to what I paid for it. They seem to hold their value pretty well.
Agreed. I bought quite a fes last summer at $375, a rate I can't even find again today. They have held their value extremely well so far. Once the 8000 series comes out, it will be interesting to see, but it's still a very good card. I would be interested to see how well you can keep a 7990 cool, and if you could really get 2 x 7970 hashing rates. My understanding is it's basically twice the power at more than double to cost, so just doesn't make sense to me unless you only have a limited number of slots to fill and plenty pf PCI Express connectors available on a nice PSU.
Per the post from LaudaM below, my 7970s are OCd to 1125 (anything beyond that, they get too unstable to be worth it), and I am between 690 - 695.
Cheapest 7970: Newegg $399 - 600MH/s average.
Cheapest 7990: Newegg $899 - 1200MH/s average.
Depends how much you can invest. Note: there might not be product available now at those prices.
Cheapest 7990: Newegg $899 - 1200MH/s average.
Depends how much you can invest. Note: there might not be product available now at those prices.
I just figure that I should get a 7970 or 7990 because if asic really does come out I can always sell the 7970 card on eBay or something probably for really close to what I paid for it. They seem to hold their value pretty well.
It's rather simple, a 7970 should give you around 600 MH/s, with the right flags and bit of OC i think you should get 700-750MH/s atleast.
That's decent
That's decent
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