I notice there haven't been a lot of replies to this thread lately, so I'm not sure if anyone is still messing about with these Antminer S2's or not. But, I'm having a bit of a problem with successfully overclocking my Antminer S2 that I bought a few months ago and I was hoping some pointers from this forum might get me on the right track.
I was actually overclocking my Antminer S2 with some success on the STOCK power supply (1,000 Watts Enermax). I took the clock frequency values posted on the first page and played around with them and found I had the best luck with 216M (215.625 MHz per chip). With this setting, I had increased my average hash rate on the miner from around 1,008 GH/s or so stock to around 1,092 GH/s overclocked. My hardware error rate only increased to 0.96% or so (under 1%, so not bad...) and I was even getting mining pool side hash rates reported from this machine in the 1.09-1.12 TH/s range!
But, I wanted to see if I could get more out of it than that. I had read on this thread that if you wanted to overclock the Antminer S2 more, you would need to get a bigger power supply so you could supply all the ASIC chips with more power to run them at a higher MHz clock speed. I also read that the ASIC chips used in the Antminer S2 are the same ones that were used in the Antminer S3, but that there were fewer chips per board on the S3 and they were running at 400 MHz instead of 200 MHz like they are on the S2. So, in my mind, I figured that if I was able to supply more voltage and wattage to the boards in my S2, theoretically I should be able to overclock the chips to 250, 300, 350, or maybe even 400 MHz and try to approach 2TH/s with my miner!
However, unfortunately that has NOT been the case! I purchased a LEPA G1600, which is a 1,600 Watt continuous (1,700 Watt peak power) fully modular power supply to swap into my Antminer S2. I completed the swap Tuesday night (March 31) and have been playing around with the chip frequencies and voltages since then and I just CANNOT get it to run any better than it already was on the stock power supply at 215.625 MHz chip frequency!! What gives here?
I tried being overly ambitious at first and jumped the chip frequency right up to 250 MHz, but it would not even hash at that speed at all! I was only getting 32-45 GH/s reporting out of the machine and I had hardware errors in the 154-175% range! This was crazy! How could such a relatively small increase basically break my miner and it wasn't working at all?! I should have the power to back up this increase in chip frequency, right? Then I tried backing it off to only 225 MHz, but that didn't seem to work much better either. I was still getting hash rates below 100 GH/s and hardware errors in the 75-120% range. This is ridiculous! Then I tried backing it off to only the 219M (218.75 MHz) chip frequency and even at THAT setting I was getting a worse hash rate and more hardware errors than when I was running it at 215.625 MHz!
So, I switched my settings back to the 215.625 MHz chip frequency for now and I am still running at 1,092 GH/s average for the time being. But it just bothers me that I was able to get that on the stock power supply and now that I have severely beefed up the power supply in it, I am unable to get any more output from my miner through overclocking it. What gives? Am I more limited now by cooling than I am by power? The weird part is, even when I tried running it at 250 MHz, my reported board temperatures weren't any higher than they were at 215.625 MHz! They were still reporting between 49 and 58 degrees Celsius, which is what they are reporting when the chips are running at 215.625 MHz as well. So, it didn't seem like they were overheating and throttling back to me at least. Is there some built-in limit that they programmed in so the miner won't run at all at higher frequencies? Maybe there is a limit to how much power can be transmitted to the boards through the PCI interface and that is where it is choking now? I notice that the Antminer S3 and S5 boards have power connectors that plug right into the ASIC boards themselves. However, on the Antminer S2, the power plugs into the big controller board that the 10 ASIC boards plug into through PCI slots. Could that be part of the problem?
I would really like to have my purchase of this massive power supply for my Antminer to not be for naught. Does anyone know if it is possible to get more out of these Antminer S2's or am I pretty much at the limit of what it can do right now for some reason? Do I need to modify the voltage field in the Advanced Miner Configuration settings in order to successfully overclock it further? I have tried changing that setting from the stock 0725 volts to 0750, 0800, 0850, 0900, and even 0950 but it didn't seem to make any difference. If this value is somehow actually used to do something, I'm kind of wary of setting it to a value over 1000, but something tells me that this value is not used since I don't see any difference in the way it mines regardless of what value I put in there.
Any help towards maxing out my Antminer S2 would be greatly appreciated! Thanks in advance and I look forward to any advice you guys can give me!