Real noob question!

[Winstar]

Hi all,

i've been looking around this bitcoin thing for a while, i also made some experiments in mining about an year ago, but I had not the hardware (i have an Nvidia capable of only 70Mh ) so i gave up.

But my question is this: is the mining a probabilistic thing? May I run a miner and be lucky and find a block in the first 10 minutes, and on the other hand i could also run for a year and obtain nothing?

What does exactly mean the value of "0.25 btc/day" calculated with bitcoin calculator, considering that a block is made of 25btc? Does it mean that, on average, i'll find a block each 100 days, but I can also stay an year without finding one if I am unlucky?

thanks a lot.

[tkbx]

Exactly. If a mining calculator says 1 BTC a day, you should get a block of 25 every 25 days or so. It's random, so you could get 3 blocks (75) on your first day, or you could go a year and get nothing.

[Winstar]

So, i could spend years making the same calculations another (and much more powerful) miner somewhere in the world has already done? I guess there is no guarantee that my mining software will try to do bitcoin calculations different from any other else in the world... am I wrong?

[deepceleron]

http://we.lovebitco.in/mining/

You will not find the same hash as anyone else, different miners will have different information in their blocks, including the address the reward gets paid to. The only competition is if miners simultaneously find a block solution for the same block number - the miner who can communicate it to other mining nodes the fastest will likely win.

Unless you have a room full of equipment, you will likely join a mining pool, which will give you regular small rewards based on your work, removing most of the variance. With a average consumer video card (like a HD 5770, 200MHash/s) solo mining is an extreme example of a lottery:

Probability	Time
Average	1664 days
50%	1153 days
95%	4985 days

There's a 1-in-20 chance that your first block won't be found for 13 years, and that's if the network difficulty never goes up (we know it will double or quadruple in the next year just based on ASIC orders). You could also get lucky and mine a 25 BTC block sooner than the several years it would take to earn 25 BTC from a pool.

[Gabi]

Yes you are wrong. Every miner does different calculations, because some part of the mining involve a random number.

The bitcoin calculator tell you that with your hashing power you will make 0.25btc per day. Yes, a block is 25btc+fees, but that only matter for solo mining. Pool mining exists, where the reward is divided between all the partecipants. So, if you pool mine, you will really make 0.25btc per day.

But.. if you make 70mhash/s, there is no way you can make 0.25btc per day 

[AndyPhillips]

It's just like mining or panning for gold: you can go for days, weeks, or months getting very little.  Then suddenly hit a pocket full of gold and make up for all the lost time finding nothing.  A roll of the dice each day.

[Winstar]

Thanks a lot guys, I did not think I could pass 4000 days with no bitcoin mined. Things are worse than I expected.
BTW, me and a couple of my co-workers (we work in the IT) are thinking to invest something in the bitcoin world. I can say we roughly have a budget of $3000 to "gamble"... what do you advice to do? Well the dream would of course buy an ASIC but if I understood well, the only shipping company is the Avalon, and their third batch is only for BTC (and at current prices 75BTC is an absurd price) so there is no open access to ASIC market.
So, what to do? FPGA? GPU?

[plastyc]

So, what to do? FPGA? GPU?

FPGA is more efficient than GPU (see e.g. https://en.bitcoin.it/wiki/Mining_hardware_comparison)
So FPGAs will stay profitable longer, but on the other hand it will be more difficult to sell a used FPGA than GPU.

I currently use 10x ZTEX 1.15y FPGAs for mining btw...

[Winstar]

So, what to do? FPGA? GPU?

I currently use 10x ZTEX 1.15y FPGAs for mining btw...

Are you telling me you are running $13k+ hardware? (based on wiki price)

Is that profitable?

[DeathAndTaxes]

Thanks a lot guys, I did not think I could pass 4000 days with no bitcoin mined. Things are worse than I expected.

That is why most miners join mining pools.   Most pools have >1TH/s and will find a few blocks a day.  Even a bad stretch might only mean finding one block every other day.  Now you don't make any more (and some pools charge fees so you make slightly less) but it does reduce the variance.  Essentially the miners are pooling resources and when a block is found they "split" it.  Exactly how they split it depends on the algorithm the pool used but it all evens out in the end.

So using your calculator stats it is something like this
pool mining: 0.25 BTC per day (minus fees)
vs
solo mining: ~1% chance per day to solve entire block worth 25 BTC

[plastyc]

Are you telling me you are running $13k+ hardware? (based on wiki price)

Is that profitable?

The price wasn't that high - there were some bundle discounts...
Yes it has been profitable for last 5 months and I guess it still will be for next few months at least.