I have an Antminer S1 and an Antminer C1. They both work as advertised and achieve a three hour hashrate average of 200 Ghash and 1000 Ghash, respectively. However, within any given second they hash within 15% of that average. So the C1 right now is hashing at about 850 Ghash, but I've seen it has high has 1150 Ghash.
I thought perhaps that the S1 did it because it is overclocked. But the C1 is not overclocked. I also think perhaps that my source for the stats might be the problem, which is the Eligius stats page for my miner.
Is this kind of fluctuation normal? Why does it fluctuate like this? Is this specific to Bitmain hardware or does other hardware do it too? If it is not normal, what could be the problem?