Quote from: Epoch on January 21, 2015, 04:05:20 AM

Quote from: bgibso01 on January 21, 2015, 03:15:51 AM

Quote from: Epoch on January 21, 2015, 01:33:18 AM

Or, as the artificial intelligence WOPR concludes in the the 1983 movie WarGames, sometimes "the only winning move is not to play."

Okay, that I understand

So I was just using an arbitrary $.10/kwh rate. You are saying there may be a sweet spot where rates are high enough that it would make more sense to run underclocked rather than stock. I'd have to see hard numbers to get it when trying to compare apples to apples. For the additional capital outlay, I don't see the underclocking making up the difference in a reasonable time. Since in my example I'm going to pay the same amount for electricity whether I'm using underclocked units or stock units I'm having a hard time seeing the underclock advantage for best dollars spent.

It is good that you are going through the mental exercise. Consider this scenario using an SP30 as an example (SP20 values will of course be different, but the concept is the same) at various underclock settings:

BTC exchange: $220USD/BTC
electricity charge: $0.10/kWh
difficulty: 44 billion
4400GH/s; 3000W; $332.14/month gross; $216.00/month electricity cost; $116.14/month profit
4000GH/s; 2320W; $301.94/month gross; $167.04/month electricity cost; $134.90/month profit
3350GH/s; 1760W; $252.88/month gross; $126.72/month electricity cost; $126.16/month profit
2870GH/s; 1392W; $216.64/month gross; $100.22/month electricity cost; $116.42/month profit
2590GH/s; 1232W; $195.51/month gross; $88.70/month electricity cost; $106.80/month profit

So if you happen to have an SP30 and you are being charged $0.10/kWh, it should be clear that you are best off underclocking it to around 4000GH/s. Your monthly electricity charge will be $167.04 on an income of $301.94, netting you a monthly profit of $134.90 per month. That's about the best you can do under those conditions with an SP30.

Let's say you buy 4 SP30's and run them at stock. That is, 4400GH/s using 3000W each (12000W). You can expect each one to net you $116.14 monthly; so for all 4 you will earn $464.56 per month. 4 SP30's will cost you roughly 4x $2000 or $8000. So (assuming BTC value stays the same and difficulty remains the same) it will take you $8000/$464.56 or 17.2 months to recover your investment. Not particularly good.

Now let's say you buy 5 SP30's and underclock them to 4000GH using 2320W each (11600W ... very close to the 12000W above). You can expect each one to net you $134.90 monthly; so for all 5 you will earn $674.50 per month. Now, 5 SP30's will cost you 5x $2000 or $10000. So it will take you $10000/$674.50 or 14.8 months to recover your investment. This is better than what the 4 stock SP30's can do.

So for this example, with the assumptions and costs as above, 5 underclocked SP30's will recover their $10,000 cost sooner than 4 stock SP30's can recover their $8000 cost. In other words: you are better off underclocking in this scenario. I haven't run the numbers for an SP20; I'll leave that to you. But it seems you've already run the analysis.

Most folks will have an electricity rate higher than $0.10/kWh so their net monthly profits will be lower, their recovery time will be longer, and the "sweet spot" will be an even more aggressive underclock.

I see that DiCE1904 has provided a handy table of SP20 values.

Nice calculation, if there is also a variable of electricity cost, then it will make a contour map to show the sweet spot of the voltage settings under different electricity charge

And, another variable is the amount of mined bitcoins that is being sold immediately. Pro-bitcoin miners never sell more than 10% of mined coins per year, but pro-fiat-money miners might sell majority of their coins right away