Bitcoin Forum

I've been looking into Bitcoin for a while, and I've made very little in my stay in the community. I was lucky to mine for about .75 BTC last time I was mining back in March, but now my poor 5770 just can't keep up.

I'm thinking about investing in possibly 2 or 3 6990's (My current mobo will take 2 easily) and then OCing them to the highest possible hash rate without putting them in danger. According to the Hardware Comparison Chart, someone with 2X 6990s was able to get 1700 MH/s with what appears to be minor OCing. At the current exchange rate, I would on average make 1.24 BTC in 24 Hrs and 37.69 per Month ($632.41.)

Barring market fluctuation and difficulty spikes, I could make the cost of the 2 cards back ($1540) and more in about 2 and 1/2 months running 24/7 (Excluding the cost of electricity.) Does this appear to be sound, or are there details I'm missing out on?

Don't forget cost of air conditioning. These video cards are rather effective space heaters so if you don't live in a completely cool climate you'll be paying about 40% of the total electricity consumption of the card to cool the room back off. Also, I don't have an exact MTBF (mean time between failures) for the cards but they'll be obsolete long before they fail - consider them to have a 12 month operational lifespan at most. Take the total cost of the cards and divide by 12, subtract this number from your monthly costs.

Find out how much you get charged for electricity and do the math, it might be more than you think too.

We would be running the rig(s) out of my workplace with their permission. So electricity and A/C are less of an issue (They'd be fully aware of the costs). Assuming the cards don't fail in the 2 1/2 months it takes to pay them off, then it's a profit for me.

1.24 BTC in 24 Hrs at this difficulty (1,379,223), in about 980 blocks the next difficulty (http://bitcoinwatch.com/) will increase by about 12% (1,544,352), and that will drop.

Plug your numbers into the link below and look at the numbers and the graph. It is only a guide, nothing is certain the exchange rate could go up (or down) the next difficulty could increase more than 12% (or drop)

http://striketeam.ath.cx/btccalc/btccalc.php
 
Growthrate in %: 1.12
Hash rate in Ghash/sec: 1.7
USD Exchange Rate : 16.80949 (http://bitcoinwatch.com/)

To make $1540 (excluding power and cooling) you are looking at closer to 5 months, unless the price of Bitcoins increases or the difficulty decreases to less than a 12% growth rate.

EDIT: The estimate on the next difficulty has already increased to 13% and will probably end up higher looking at the current rate of hashing growth (http://bitcoin.sipa.be/growth-10k.png)

Thank you for providing that calculator! Taking all that into account, I'd be better off buying 2 5850s (Found them for $125 after shipping). I could pay off the cost of the cards in a little over a month! Albeit the net gain isn't as substantial...I could still make a profit!

Any idea what the growth rate may be after these few months?

No one knows, it depends on how many people are interested in mining, which has only been growing exponential since day one from what I see. My GUESS would be the next increase will end up somewhere between 20-40%. Look at  the historical graphs (http://bitcoin.sipa.be/) It looks like the growth has slowed down over the last two weeks, but not by much.

Thank you for your insight. I'll consider purchasing the lower end card and seeing if I can at least get my money back for it.

I suggest you follow your own calculations, and don´t believe a word of your direct competitors.
too many shameless biased opinions ...

It is not my calculator. When I started mining about two weeks ago, I wish I knew as much as I do now. I'm just warning to be prepared for a more realistic payback time frame on graphic cards. I made the same kind of assumptions that ZeroShift made. But it is not a simple straight line calculation. And there are random factors in the exchange rate and the rate of difficulty increase. But I do agree that everyone needs to do their own  analysis of their investment/costs, risks, rewards. And in future, gusti, I will keep my mouth shut and not advise others of anything to do with mining. The only reason I joined this forum was to payforward what I had learned from it.

Trust me, I will not base my work solely on the opinions of others. I sincerely appreciate the input, and I'll forge my own path once I gain enough experience and try to draw from others.

Get a few fans and an ice pack

I plan to duct the heat outside if it becomes a problem, just like a clothes dryer.

haha me to

I have right now two 6990 and are getting around 1 bitcoin per day. Pretty good IF the price keeps rising.