Ah, so it's not directly related to hashing power but rather time to completion. Useful info-mation thank you.

So difficulty and hashing power share a proportional relationship, to double the current difficulty you will need to average double the previous rounds average hashrate. That makes me feel better about mining, unless we see some massive influx of people or some new mining tech comes about shouldn't be seeing 1mil for quite a while yet.

I'm sure there are a lot of other worthwhile replies in this thread, but I'm just going to go ahead and say that I like you. And read the rest later.

I wish that I had been born 20 or so years earlier and known that a little company called microsoft was going to blow up and buy tons and tons of their stock, or that I had been born 10 years earlier and made good buddies with the guy who started google and get a bunch of their internal stock before they went public. Or actually I guess if I could see the future I could still make a ton of money now.

Well I had this debate with someone the other day, but I'm currently running 4 5870s (@ 430MHash) on a Seasonic X750. My wall meter reads the power draw at about 783Watts to the system, so I'm slightly overloading it (it is fine but I suppose for the very long term this might not be the best idea). So an 850 should be adequate assuming you have a mining rig similar to mine.

If you are really super squeamish about running a PSU near its capacity (which seems weird to me, people don't buy 3GHz CPUs then downclock them heh) then getting a gold class PSU isn't actually that bad an idea, when running huge loads the efficiency actually begins to actually save you money, depending on your power rates.

The english in this thread is a bit confusing, so I will just make some statements and if they're not totally on topic I apologize.

First, it is very easy to set something like this up, there are even cheap little buttons you can buy for like $5 to basically be an on switch for both PSUs.

Here is one of the eaiest guides I've seen on the subject: http://www.overclock.net/power-supplies/14455-multiple-power-supply-guide.html

Now with that said my suggestion is: Don't do this. It can have some problems which are obvious and ones which aren't so obvious (like imbalanced grounding). This is just a suggestion of course.

I am running 2 5870s and a 5850 on a single x650, and my power meter reads off their consumption for the entire system at 550W. I don't suppose 3 5830s uses more power than that, so I would be comfortable in recommending a 650Watt power supply as enough for 3 5830s (assuming you downclock the memory and use an efficient and small CPU like me, I am using a 45W sempron). An antec Earthwatts 650 can be had for $65 last I checked. That's pretty reasonable for a good PSU.

I don't feel qualified to rate PSUs, so I leave it to the experts. HardOCP is typically considered a reputable review source and they say:

http://www.hardocp.com/article/2011/02/23/raidmax_rx1000ae_1000w_power_supply_review/9

That it is a pass (pass in this case actually means really good and reliable, not the best necessarily but it should handle what it says it will handle).

That's actually a pretty good price for a PSU of that quality and size so I will save you from my usual speech about spending too much money on an oversized PSU.

enjoy!

No, no reason other than resale value to buy 6990. Well 1 reason, if you want to game on it as well as mine. But for dedicated mining the 5970 is by far the superior buy (if you can find it).

I'm guessing the beer comment is a comment in jest, as the costs to operating a pool are significant.  Transaction fees are part of block solving as I understand it, so yes the solo miner, or pool involved gets the transaction fee. I don't think pools pay them out so it is a bit of hidden cash out to the operator. Looking at BTCGuilds stats though, it's not really that significant, 24BTC of transaction fees in 14,000BTC of block solving.

As far as I know there is no requirement to pay anything for transactions, although some client versions might have that built in, I know that mine does not.

Won't assrape the planet either (as badly), if that means anything to you.

If you are going to be getting extenders anyway you don't really need to get double spaced x16 slot motherboards. You can get much cheaper motherboards with 5  cramped together x16 and x1 slots, and just use extenders to space them out.

This may seem obvious but how is the difficulty calculated exactly? By which I mean what is the algorithm not the basic concept. I know the idea is to be able to mint 50 bitcoins every 10 minutes but I'm not that familiar with hashing concepts. I've been curious about hashing rates vs. difficulty increases for a bit but I haven't seen the way it is calculated.

If not the precise algorithm (as it may be calculated in a complex manner) a way to roughly estimate would be helpful.

We should do about DDoSing what everyone should do about DDoSing.

If I upload/download a britney spears song via a torrent I can potentially be liable for tens of thousands of dollars in "potential lost revenue" after my ISP surrenders all my information, but if a real functioning entity is actually prevented from having an online presence on the internet because my connection is part of a collective effort to bombard it off the internet, that's no problem?

Should start a lobby to get ISPs to knock zombie machines off the network until they can pass a scan showing they are no longer infected. Yes I know there's lots of international stuff too, doesn't seem a difficult program to institute worldwide.

If you think your luck will continue to hold, then that indeed might be a good option. Myself I've found as far as I know 0 or 1 blocks in a month of 3GHash mining. Let's just say I made far more BTC than that

My advice, don't buy any of those. Those are awful awful prices. Unless you live in the UK and you're converting GBP to USD. If you live in the US just pop over to newegg.com and buy some 5830s, $109.99

Deepbit is the largest pool which has the advantage of breaking blocks at a pretty consistent rate (lowish variance), pays out instantly (no confirmation), pays for orphaned blocks and stale shares, has a nice user interface and if you worry about variance has a nice pay-per-share option for steady income.

On the other hand deepbit is the largest pool which makes it a constant threat for breaching the magic 50% barrier (kind of against the principle of bitcoin), makes it a target for DDoSing disrupting mining, has the largest fees of any pool and probably some other drawbacks I can't think of offhand.

I encourage people to use deepbit, but I also definitely encourage people to use the other very respectable and profitable pools, or go mine solo, especially because of the 50% of network power problem. I don't care that Tycho is making mad money off his pool, he worked hard, opened a lot of doors for bitcoin miners and other pool operators in general, and set up one of the best pools around. If he makes some bling off it, good for him.

My other favorite pool at the moment is btcguild, though I've heard good things about swepool and miningpool(?) and so on.

One way in which 6990s win out is future re-sale value. They have staying power that 5830s likely do not. If you worry about BitCoin going bust in a year or so, and you find yourself with say 4 5830s, you might find yourself hard pressed to drop them as they fill kind of a weird niche (weak graphic power, high temp and power consumption at a price point that puts it against cooler sleeker used gtx460s). while a 6990 is likely to be a hot commodity for couple of years to come.

But it's unlikely that this will really be enough to tip the scales in the 6990s favor. I personally consider it to be one of the worst buys one can make other than say nvidia. For pure hashing the 5830 is the king of MHash/$ if you can stand the noise/heat/elec bill.

Why does china need to mine to buy bitcoins in RMB? What you need is for someone in china to set up an exchange.

I'm not familiar with linux so I can't help you from that standpoint but I will say it is not due to the pool. GPU load for most pool miners is 95-100%.

Try to make sure whatever the equivalent is to an "aggression" flag is set as high as possible.

I'm still waiting for proof of this claim I've seen multiple times.

For example: http://www.techpowerup.com/forums/showthread.php?t=100993 is a 6 gpu setup running under windows. 3 physical cards, 6 physical cores.

http://www.maximumpc.com/forums/viewtopic.php?p=931366#931366

This fellow is running 4 dual core cards, again 4 physical cards, 8 physical cores.

http://hardforum.com/showthread.php?t=1492462 suggests that 8 physical GPUs is the limit, but no real sources are cited.

Some time if I get a bigger PSU and some pCI-E extenders I may solve the mystery for myself, but for now I rely on someone else to answer conclusively.

Mining is profitable and requires you to devote enough time to build a computer and then start some software. Then you can go about your life. Being tech savvy is a definite plus however.

 Given the recent price fluctuations buying coins is still more profitable however. This may change in the future, who knows.

Based on what? MtGox alread ywent down to DDoS sometime last month for extended period of time. There was no crash (admittedly there was a price bump when it came back up).

Sadly the best post in this thread was about the difficulty in setting up an exchange, not due to technical reasons (this is easy as pie) but due to the legality of such an exchange. A huge portion of bitcoin users exist in a country where legally they would be at huge risk if they set up an exchange.