A theoretical 2x6870 rig @ 600MHash/s combined.
(233 * 2.16) / (0.450 * 0.21) = 5325.71...
244139.48158254 / (6.44 * 50) = 758.197...
Something doesn't seem right (It is 4am, though... nothing seems right when it's 4am)
Topic: What's your magic number? (or, Should I keep mining?) - page 3. (Read 8752 times)
Mine is 16,776
The current difficulty value for GBP (based off Britcoin ask rates) 244139 / (£3.85 * 50 BTC) = 1268.25 (shouldn't this be Shares/GBP?).
Absolutely right! A share is just a hash that would be valid at difficulty 1. I've edited the post to use this terminology.
My magic number is around 16,731 using a single 5870 with a hash rate of around 375Mhash/s (1.35 Thash/hour) - I have discounted the power requirements for the other components since the PC would be on pretty much 24/7 anyway (its not a dedicated miner) and as such the mining is only costing me the extra GPU power (0.188 kW) draw at a rate of £0.10 kWh. (Infact it is probably reducing my heating costs 
)
The current difficulty value for GBP (based off Britcoin ask rates) 244139 / (£3.50 * 50 BTC) = 1395.08 (shouldn't this be Shares/GBP?).
Last Update: 18:40 BST 21st May
Edit: I've decided to calculate my magic number including all other components and internals, cooling etc, which all in all uses around 350W (Core 2 Duo E5200 @ 2.75, 4x1Gb DDR2, Assorted drives).
( 1.35 Thash/hour * 233 shares/Thash ) / ( 0.35 W * £0.10 ) = 8987.14
A much lower number once I included all the internals and USB stuff also drawing power; however I would probably keep mining up until the 16,000 mark simply because the other components would be turned on regardless since this is a desktop machine and I don't count their cost off my BTC profits.
)The current difficulty value for GBP (based off Britcoin ask rates) 244139 / (£3.50 * 50 BTC) = 1395.08 (shouldn't this be Shares/GBP?).
Last Update: 18:40 BST 21st May
Edit: I've decided to calculate my magic number including all other components and internals, cooling etc, which all in all uses around 350W (Core 2 Duo E5200 @ 2.75, 4x1Gb DDR2, Assorted drives).
( 1.35 Thash/hour * 233 shares/Thash ) / ( 0.35 W * £0.10 ) = 8987.14
A much lower number once I included all the internals and USB stuff also drawing power; however I would probably keep mining up until the 16,000 mark simply because the other components would be turned on regardless since this is a desktop machine and I don't count their cost off my BTC profits.
When calculating the electricity cost, don't forget: everything that uses power, that wouldn't use power otherwise, is a mining cost. If my machine weren't mining, it would be sleeping and wouldn't have a window fan pointed at it.
Excellent post!
It appears my magic number is ~15,000. I'm mining with a single 5850, see if my numbers check out.
0.972 Thash/hr, 0.151 kW (based on the mining hardware comparison), $0.10/kWh.
It appears my magic number is ~15,000. I'm mining with a single 5850, see if my numbers check out.
0.972 Thash/hr, 0.151 kW (based on the mining hardware comparison), $0.10/kWh.
Watching the difficulty go up, I realized I needed a way to quickly recognize when the day comes that mining is no longer profitable. So I worked out the following. Maybe someone else will find it useful.
If you are a miner, your your "magic number" is M = (shares * hashes) / (power * cost), where
All of these numbers are relatively fixed, so go ahead and calculate your M now. Be sure you have the units straight---this "number" is actually denominated in shares per. In fact, it has a specific meaning: it's the number of difficulty 1 shares you are generating per spent on electricity. Using the data above, for example, my magic number is about 9700 shares/USD.
The point of this exercise is that your mining is profitable on the margin if and only if M > diff / (xcg * reward), where diff and xcg are the current difficulty and exchange rate and reward is the block reward (50 BTC right now). So when difficulty increases and you're wondering whether to keep mining, or the exchange rate soars and you're wondering whether it's time to fire up the ol' CPU again, you now have an easy way of deciding. Just divide difficulty by exchange rate and reward, and compare it to your magic number.
For example, right now we have a cutoff of (244139 shares/block) / (6.63 USD/BTC * 50 BTC/block) ≈ 735 shares/USD. Anyone whose magic number is lower than this shouldn't be mining. Fortunately, mine is still well above it! Unless the exchange rate tanks or the difficulty soars, I should still be in the game for at least a couple of months.
If you are a miner, your your "magic number" is M = (shares * hashes) / (power * cost), where
- shares is the (constant) rate of "share" generation per hash, which is about 0.000233 shares/Mhash or 233 shares/Thash;
- hashes is your hashing rate versus time (say 780 Mhash/sec or 2.81 Thash/hr);
- power is your rate of energy consumption for mining (say 450W or 0.450kW); and
- cost is your cost of electricity (say 0.150 USD/kWh).
All of these numbers are relatively fixed, so go ahead and calculate your M now. Be sure you have the units straight---this "number" is actually denominated in shares per
The point of this exercise is that your mining is profitable on the margin if and only if M > diff / (xcg * reward), where diff and xcg are the current difficulty and exchange rate and reward is the block reward (50 BTC right now). So when difficulty increases and you're wondering whether to keep mining, or the exchange rate soars and you're wondering whether it's time to fire up the ol' CPU again, you now have an easy way of deciding. Just divide difficulty by exchange rate and reward, and compare it to your magic number.
For example, right now we have a cutoff of (244139 shares/block) / (6.63 USD/BTC * 50 BTC/block) ≈ 735 shares/USD. Anyone whose magic number is lower than this shouldn't be mining. Fortunately, mine is still well above it! Unless the exchange rate tanks or the difficulty soars, I should still be in the game for at least a couple of months.
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