Quote from: LeeC on February 15, 2015, 01:58:52 PM

Right now, all SP20's have their fans set to auto and i can see they are all pulling somewhat the same mining rate. Their temperatures aren't very different but over the last 5 minutes I have units reporting 1428, 1586 and 1865 . This is quite a difference and i see it reporting that rate to MRR too [...]

The only thing i've changed of late was my pool , but this was done at MRR and not locally. I switched the 'when not mining' pool to CKPool From BTCGuide as a test. Would this pool change have had any effect on the local hash rate of the machine (i don't think so) If not any ideas ?

The hashing speed as seen by the pool is a function of the high difficulty (as set by the pool) shares solved in a given amount of time, with respect to the theoretical time in which a share of that difficulty would be solved in ideal conditions (i.e how long it takes to solve a share).

The hashing speed as seen by the mining unit is a function of the low difficulty shares solved by the unit determined with respect to the logged clock speeds, hardware errors etc.

This is why you see your SP20 determined hashrate at 1.5TH and on the pool "calculated" at 1.8TH. That means your miner was rather lucky over the interval monitored by the pool and solved a little more high difficulty shares during that time. Sometimes the pool speed is lower than what your miner says, and that means you miner solved less high difficulty shares over the averaging time ..

Now, if you switched pools, different pools have different running averages .. in short term you might see fluctuations on the speed as detected by the pool. They cancel out over a large time span, if you keep your settings constant.

If you look at Burnside's calculator (http://ltc.kattare.com/calc.php) you can reverse the equations to tell you the hashrate as a function of time ..
There, they calculate the value of the shares based on the theoretical difficulty (block find speed).

Code:

fee = elem(coin + "_fee").value / 100.0,
   gh_per_sec = elem(coin + "_mhs").value / 1000000.0,
   coin_usd = elem(coin + "_usd").value,
   coin_btc = elem(coin + "_btc").value,
   usd_kwh = elem(coin + "_usd_kwh").value,
   watts = elem(coin + "_watts").value,
   cost_day = (watts / 1000) * 24 * usd_kwh,

   // Calculated Values
   coin_per_share = (1 / diff) * (value - (value * fee)),
   shares_per_day = gh_per_sec * (1 / gh_per_share) * sec_per_day,
   coin_per_day = coin_per_share * shares_per_day,
   time_hour = ((gh_per_share * diff) / gh_per_sec) / 3600,
   time_day = time_hour / 24,
   usd_profit = (coin_per_day * coin_usd) - cost_day;
   usd_gross = (coin_per_day * coin_usd);
   btc_gross = (coin_per_day * coin_btc);