40e6 (watt) / 0.06 (joule/gigahash) / 1e6 (petahash/gigahash) = ~650 petahash/second
BitFury's immersion cooling tech:
https://www.youtube.com/watch?v=uV7MDhqNyXE&t=0m42s (shows the fluid boiling - starts at 0m42s)
BitFury's 16nm chips:
Plus, with BitFury online, the cost of a 51% attack just raised to $200 million.
The only reason it is (currently, for a short time) hypothetically possible to 51%-attack the network with a budget in the low hundreds of million of dollars is because most of the miners are not using such efficient 16 nm chips. As the market migrate to these last generation chips, expect the cost to increase to $1+ billion in the next year.
If BitFury can turn $200 million into $400 million now rather than over a couple of years, why on earth would they care about the side-effect of killing off bitcoin?
For the avoidance of doubt, I think that BitFury's best interest is BitFury; as long as they make a decent chunk of money, the end result for bitcoin is - and should be - immaterial to them.
Would they even need to convert BTC into USD? Even ignoring the obvious opportunities for shorting an entire economy?
I mean, I'm kinda curious to know what effects they could cause by e.g. choosing to mine zero-block transactions for a few days.
If they find the next block during the time they are mining only against the block header, that block will contain no transactions. This doesn't happen very often, and there are some other issues that can arise from the practice (a multi-block fork happened once), but miners believe that it increases their profitability so (afaik) they continue to do it. More info here: http://bitcoin.stackexchange.com/questions/38437/what-is-spv...
Why would the price plummeting matter to them if they've already made their money?
Not if their cash isn't - somewhat ironically - tied up in BTC.
Really, I'm sure between the two of us, we could imagine a thousand and one viable ways of making a tonne of cash very, very quickly that wouldn't involve transacting in BTC at any point!
You can cripple Bitcoin transaction clearing with a thousand dollars to DDOS the network with spam. If only state-level actors had a thousand bucks lying around ...
So they can "unspend" their own bitcoins, as follows : use 51% of your hash power to create a parallel blockchain, which is not published. Include all transactions, except the one you used to buy a TV. Put something else in it's place. Keep doing this until the TV is shipped/arrived. Then publish the parallel blockchain. Boom. Unspent.
In any reasonable person's version of "wait X blocks for confirmation" (currently mostly 3), X would be infinite.
If they make good money from it, why would BitFury care about bitcoin's long-term outlook?
Best case scenario is that at the end of the effective life of this DC BitFury decide to doublespend their coins to allow them to spend all bitcoins once, however by that time their relative % of the network will be less than 50%.
Why not? Surely this is more a lack of imagination on your part, rather than a hard fact?
* During the transaction spam DDOS attacks, the price went up even though it was literally unusable.
* The present price seems sustained by something that looks very Willybotish running between OKCoin and Huobi. https://www.reddit.com/r/Buttcoin/comments/3vnjgk/what_drive...
The remaining American Bitcoin traders are certainly gullible enough to keep buying and trading a 51%-compromised coin. (I mean, there are people who still think Paycoin could make a comeback.) But American traders are a sideshow - all the action is in China (miners, actual traders). So the question would be: will Chinese speculators keep gambling on a 51%-compromised coin?
(And of course the MMM ponzi buyers, whose judgement is sufficiently bad that they wouldn't even understand the problem.)
No, this post, and the handy table inside, explains the various attacks possible at different percentages of the hash rate:
50MW is enough power to supply ~14k homes from different references I've seen.
I'm curious about what normal data centers use for backup power since natural gas and diesel generators don't get much bigger than 2MW. Or maybe they just don't have backup generators.
They have gas capable engines (50DF series, 50cm cylinder bore) with ratings up to 975kW/cylinders and up to 18 cylinders or 17MW per genset at 60hz.
They're not the only player in that field. Fairbanks-Morse sells the Colt-Pielstick PC2.6 line with 750kW per cylinder at 600rpm and up to 16 cylinders for 11.5 MW @ 60hz. They also sell MAN 48/60 engines that go up to 21MW and MAN natural gas 51/60 G engines up to 18.5 MW.
 This also means that putting 650 Phash/s gigs into the network is not as profitable as it seems, since it will double (55%) the ratio while three times more expensive (if it linearly scales).
It doesn't really matter how high the difficulty is or who the miner is the coins are mined and most of them sold.
There might be a small fraction of coins which are still mined in pools using outdated miners and those people don't bother selling them coins(fractions of coins that is).
It has been accepted wisdom that most mining operations sell most/all of their mined coins.
I'll look for that article now.
EDIT: Not the article I was looking for, but it covers it and was from 2013. This guy was using the cheap Icelandic power and the cold Icelandic air to his advantage.
What you describe is price-based competition. It’s probably the most documented situation in economics, and it present in many markets. It is a race to the bottom, but rarely ever ends; when it does, it is generally by disruption (something people on HackerNews know a lot about). In the mean time, it drives technical innovation after technical innovation—but I doubt, after 40 years of Moore’s law that it will suddenly end.
* The constant amount actually changes periodically when the coinbase reward is adjusted downward but that only happens about once every 4 years and historically exchange rate price appreciation has outstripped the reduced coinbase mining rewards. eventually the coinbase reward will go to zero and the number of coins that go to miners each day will be their relative share of the total fees being paid by users transacting on the network. Miners choose which transactions to include in a mined block so in the future a large miner may have some pricing power over transactions because they could refuse to process any transaction with a fee that falls below some threshold.
To put this into context, by comparing it with a centralized version, an equivalent number of actual transactions could be done at a bank with a crud app running on a $5 complete desktop PC which the Raspberry Pi foundation just released. It is a 1 ghz computer with 512 MB of RAM. It draws up to 0.7 Watts.
Wait, wait, wait. did I say an equivalent number? Since Bitcoin is limited to 7 TPS (7 transactions per second), I should modify this to 100x more transactions (700 transactions per second), if you wrote it in C, or if not a hundred times, then at least ten times as many in python. If it were a crud app running at a bank, a $5 computer could do 100 times the transactions that 650 Phash/s of wasted effort collectively give. And 40 megawatts.
But it's a stupid, wrong solution. The basic idea sucks. It's bad.
(by the by my target price for btc is $600,000 based on a comparison with how bad gold is physically, and the market cap of gold. :-P.)
I love fiat currencies, they're one of the great achievements of modern civilization. (This sentence isn't ironic, it's actually how I feel.) Despite my target price I don't hold any bitcoins at all. I hope some of the numbers I've given can put into perspective why.
> But it's a stupid, wrong solution. The basic idea sucks. It's bad.
instead of explaining that the cost is the cost of guaranteeing the authenticity of the transaction. HackerNews likes technical comments, and will happily burry expletives.
You could find more compelling example, such as estimate the ecological cost of having most of the current world-wide banking transactions on BitCoin, and prove your point.
Also, you don't seem to understand the point of PoW.
No, you're being downvoted by technical people because you're missing the whole point of decentralized digital currencies. Educate yourself: https://en.wikipedia.org/wiki/Cryptocurrency#Timestamping
> I love fiat currencies, they're one of the great achievements of modern civilization.
Yeah, unless you want to export some Cuban cigars from Germany to Denmark: https://en.wikipedia.org/wiki/Society_for_Worldwide_Interban...