What's your magic number? (or, Should I keep mining?)

[adlin5000]

I'm new to this (just saw the write-up on lifehacker), and curious if this would be profitable. I did a test run on my q6600 using only two cores and got 2269 khash/s. Now at .14 kWh and a 450W ps I got .008391698 as my magic number. Now assuming my math was right (.000233*2.269)/(.45*.14) I should just forget it.

My questions are:
1. Did I get the math right?
2. Would using a mining program vs bitcoin make a difference?
3. Would using a mining program on my 9400GT card make it worthwhile?

Thanks for the help.

[1713936988]

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[Turix]

Based on the information here I can make a few of these estimates for your system under ideal circumstances.

Using the highly optimized SSE2 miner yours Q6600 should be able to do 11Mhash/s using all 4 cores for 105W, now if you only want to use two cores then we can roughly half all of those numbers for the total calculation (very roughly)

So thats 5.5Mhash/s @ 52.5W.

Next we add your graphics card in, which is sadly only capable of about 3.37 Mhash/sec at a power usage of 50W.

So the following magic number apply for you (assuming no other power use, which of is not true):

Just CPU = 585.83
Just GPU = 376.90
Both CPU & GPU = 518.43

Now as you can see I'm afraid even under ideal circumstances, not counting the cost of power for your other components/cooling/peripherals you are well below the break-even point of around 700 shares/USD right now, with your GPU being far more inefficient than your CPU.

[Gameover]

that sounds about right, mining on any CPU is pretty much worthless, they are very inefficient.  mining on my 5GHz 2500K yields 8 Mhash/s where on my 6950 is 360 Mhash/s, ATI video cards are where its at, nVidia cards are about 5-10x slower due to their GPU architecture being more like a CPU than ATIs.  You can read about it on the bitcoin FAQ.  It doesn't sound like it would be worth it for you on either the CPU or GPU.

[Turix]

Just out of curiosity I did the calculations for my Netbook (HP Mini 311c) which has an Atom N270 and Nvidia ION chipset (Geforce 9400M - hell yeah, netbook with Dx10 and Cuda  ) while they have very low hash rates I was curious to see if the silly low power usage would counter that. The hash rate testing was performed in Ubuntu 11.04, using the SSE CPU Miner and Phoenix GPU miner.

I pay about £0.10 per kWh for power.

CPU:

Hashes at 1.52Mhash/s
Draws 5W at full load

GPU:

Hashes at 1.92Mhash/s
Draws 6W at full load

However when I tested this I noticed that they cannot do these hash rates while the other is loaded as they must share some of the same components in the ION chipset, the combined hash rate was only 2.52Mhash/s.

Once again discounting all extras such as the screen, HDD, speakers, etc, etc we get the following:

Just CPU: 2549.95
Just GPU: 2684.16
Combined: 1921.61

So in this case, surprisingly in theory it is technically profitable right now to using my netbook; however once the power used by everything else is factored in (29W maximum with screen on full brightness at 100% load) with the obscene low hash rates it is completely unfeasible.

[SchizophrenicX]

Don't forget that this is assuming that you sell your BTC at the exact rate that is used to calculate (BTC/USD), if you stop once your "Magic Number" falls below, you'll stop earning BTC. Essentially betting that BTC rates will not go up.

If enough people does this and pulls out, others that are still mining will get more for their shares since less share are distributed during the solving time.

Also, you're ignoring the fact that (if) you invested capital into buying hardware and have not compensated, those are just sitting around. AND if you're just waiting for the rates to go up, you won't have BTC to sell (assuming you sold them when you've got them) when they do and have to start mining for them.

But of course, during this 'downtime' it's obviously better to use your 'cost' to buy bitcoins instead that'd bring a different dynamic as people who are still mining would earn more BTC while people who are buying bitcoins are bringing the rates up.

The important question is then how long does it take for the rates to go up high enough for people to start selling/mining again, if it takes long enough, people who are mining might make more than those who are buying as the prices go higher. If this time period is too short then question is did you buy enough to cover what you've missed out.

Then again, this is assuming if the economy get's back up. if it doesn't, then those who invested into buying more than their 'cost' would lose more, while those mining will have BTC in their wallets and maybe those will worth something in the future after the collapse.

Just my 2 cents worth, I don't really know which is better or the real dynamic. I'm new and I just think that calling this a 'magic number' is over-reaching and it actually doesn't reflect enough of what goes on. It just shows that right at this point you're probably paying more for electricity than what you're mining. Not necessarily a decisive factor to stop operation altogether.

[commlinx]

Very useful post for those intending to get into mining and/or purchasing more hardware. As I'm using some existing equipment a while ago I calculated the extra power use as about $1 a day and just keep my eye on if it's profitible from time to time based on my BTC generated per day, not as though in my case having it running a week when it would have been cheaper to purchase is a particular financial disaster.

Besides it's coming into winter in Australia and I'm having a go at growing herbs inside, so if I stop mining it'll probably get too cold and kill my Thai Basil .

[urtur]

CPU:

Hashes at 1.52Mhash/s
Draws 5W at full load

GPU:

Hashes at 1.92Mhash/s
Draws 6W at full load

However when I tested this I noticed that they cannot do these hash rates while the other is loaded as they must share some of the same components in the ION chipset, the combined hash rate was only 2.52Mhash/s.

Yeah, some resources are definitely shared.
For my machine it looks much more extreme:

Just CPU: 9.5 Mh/s
Just GPU: 85.5 Mh/s

Both: 68Mh/s(GPU)+9Mh/s(CPU)=77Mh/s - so it seems their competition for resources takes up some time. I got the highest M using GPU only.

[ne1]

Where did the shares =233Thash/hr come from?  I can't find where that is calculated.

Bitter Tea: Thanks for writing the script, but something seems backwards, when I put 15mhash it says profitable, when I put 1500Mhash its says not profitable.

[BitterTea]

Bitter Tea: Thanks for writing the script, but something seems backwards, when I put 15mhash it says profitable, when I put 1500Mhash its says not profitable.

Oops, I messed up the comparison. It should be

Code:

if(magicNumber > baseline) alert('Mining is profitable!'); ...

[frozen]

Where did the shares =233Thash/hr come from?  I can't find where that is calculated.

From the first post: "shares is the (constant) rate of "share" generation per hash, which is about 0.000233 shares/Mhash or 233 shares/Thash"

For every Thash, approximately 233 "shares" are generated. A "share" is a hash that would validate if difficulty were set to 1.

Suppose that you have a machine generating 500Mhash per second. Multiply by 60 seconds per minute = 30000Mhash per minute. Multiplying again by 60 gives 1800000Mhash per hour, or 1.8Thash per hour. Approximately 1.8*233 (419) shares should have been generated during that hour, 7 shares per minute. It will take approximately 8.5 seconds to generate a share. Double this to 1000Mhash, and it will take about 4 seconds to generate a share.

If anyone finds a mistake please let me know.

[Ian Maxwell]

frozen, what you wrote seems pretty much correct. It's worth pointing out that the 8.5 seconds is an average, and there's a significant chance that once in a while it will take a minute or longer (or a second or less). In fact, if you're mining 24/7, that probably will happen once in a while.

[ne1]

Thanks for the replies.  What I'm asking is where did the 233 in the first post come from?  How do we know it's a constant?  Is it a calculation related to the difficulty?  If the difficulty goes up, does the shares per Thash go down?
   

[frozen]

Thanks for the replies.  What I'm asking is where did the 233 in the first post come from?  How do we know it's a constant?  Is it a calculation related to the difficulty?  If the difficulty goes up, does the shares per Thash go down?
   

It is a calculation given a difficulty of 1. It is an approximation, because in practice you might get more or less.

If you have a six sided die, the odds of getting three is 1/6. But in practice, you might only have to roll the die 4 times to get a 3 instead of 6. Or maybe you'll need to roll it 13 times. But if you do try this billions of times, the number of threes as a percentage of the total number of rolls will approach 1/6.

Given a difficulty of 1, 233 is the approximate number of valid hashes you would generate with 1 Thash.

At least, that's how I understand it =)

[molecular]

Thanks for the replies.  What I'm asking is where did the 233 in the first post come from?  How do we know it's a constant?  Is it a calculation related to the difficulty?  If the difficulty goes up, does the shares per Thash go down?
   

1E6 / 2³² = 0.000233

[ne1]

Great, thanks guys!! I get it now.  With the given numbers, is there then a way to calculate what you are generating btc/hr from your magic number?

[k]

Inspired by this thread and bitcoinBull's thread http://forum.bitcoin.org/index.php?topic=7427.msg109079#msg109079 I created a graph of the cutoff number over time.



It uses the daily average price from MtGox and the difficulty level on that day.

[k]

I went a step further and did a profitability chart. Profitability = Magic number/cutoff
Ian, I used you magic number of 9700 shares/USD as an example for this chart.



If I'm interpreting it right this number shows the ratio of money you are generating by mining vs the money spent on electricity. So a number of 10 means you are making 10 times as much in bitcoins by mining as you are spending in running costs. If the number goes below 1 then mining is unprofitable. There is no consideration for initial hardware costs or depreciation or anything like that.

[Justsomeforumuser]

I am not sure why people are overgeeking this into obscure numbers.

1. Take your 7 day average of BTC generation. While difficulty remains stable, this is your current income estimate in BTC. As it adjusts, you get a new figure that should ideally remain vaguely proportional.

2. Figure out the Watt difference of your system between generating and not. This is either idle vs load if using the PC anyway, or off vs full GPU load while running if dedicated.

3. Calculate your extra / total kwh per day. Multiply by xx cent per kwh. Have a daily cost.

4. You can now calculate: At xx BTC per day income and xx cent or USD cost per day, I need the exchange rate to remain above xx USD to break even or make a profit.

5. Forget magic numbers.

[k]

I am not sure why people are overgeeking this into obscure numbers.

1. Take your 7 day average of BTC generation. While difficulty remains stable, this is your current income estimate in BTC. As it adjusts, you get a new figure that should ideally remain vaguely proportional.

2. Figure out the Watt difference of your system between generating and not. This is either idle vs load if using the PC anyway, or off vs full GPU load while running if dedicated.

3. Calculate your extra / total kwh per day. Multiply by xx cent per kwh. Have a daily cost.

4. You can now calculate: At xx BTC per day income and xx cent or USD cost per day, I need the exchange rate to remain above xx USD to break even or make a profit.

5. Forget magic numbers.

I find it interesting just to look at the numbers. I don't even mine as it's totally unprofitable for me.

[ne1]

Ok so I set up this site with a simple dashboard based off this magic number equation
http://bitcoindashboards.com
  Please check for any errors.  I will keep building on it.  The next step will be to factor in some what ifs for $ projections, ROI %, fee incorporation etc. etc. Any suggestions welcome.  Also I will pass along 10% of any donations to the original poster of this equation, Ian Maxwell .