WOW! 0.75V at 100c? I'd love to see your video! What magic you have done. I'm looking to maximise while staying under 100c.
Not magic-- I just got extremely lucky on that one ASIC. The others perform more typical for their position on the board. Getting the heatsink
perfectly level over the ASIC to close the gap is the key. That is extremely tricky to do given the small surface area. I used a thin coat of AS5 for the ASIC-to-copper heat spreading plate junction (where there is a lot of heat in a small surface area), and ordinary Thermalcote for the copper to aluminum junction (the heat is spread out there so a lower grade paste works just as well).
IMO, Spondoolies used way too much paste on the copper-aluminum junction. Also, several of my copper plates had distinct nicks on them that indicated they were never balanced properly on the ASIC to begin with, and the aluminum heatsink bottoms are way too rough. They had the right idea with a copper heat spreader before the aluminum heatsink, but the execution of it was poor. Had it been done better (4 sided with correct tension and smoother aluminum) these probably would have met their 1700GH spec.
Maybe SP20 is outdated but when you run miners in working environment, new noisy ones are out of question. I run SP20 at 0.61 to keep ASIC reporting 85c (I guess it is actually less and 85 is software lower threshold). This way fan stays at 6 with "auto" stetting and hash goes up to 980GH/s taking under 500W. Show me miner you can down-clock so far! And bought it under $150 in EU.
Interestingly, I find mine to run a bit more efficient W/GH around 100C than at 85C (my power meter reads about 25W per miner less for the same hash), but mine are all down to 85C now too due to profitability. The one I repasted shut down once from being too cold (10C intake resulted in 42C exhaust at 0.62V/6% fan and it didn't like that-- it handled 0.64V/6% better). Winter is gone now, so that is no longer a problem, but I'm still running 0.64V for the time being since the profit difference is miniscule and I'm cautiously optimistic.
Except for the eBay one, I bought mine in January 2015 during the fire sale and they are still mining 15 months later (on 0.0875/kWh power). I more than ROI'd those! Their profit is tiny now, but they will remain on until no longer profitable (which could happen any diff change now). I'll probably toss them solo for a month after that for a little fun before halving then I'll retire them. I almost sold them, but I guess there are some tax implications since I used them for more than a year which make it less worthwhile to sell them now (I don't completely understand it so don't ask me to explain-- that's what a CPA is for).
I'll see if I have some time in the next week or two to edit that video. It's been a bit chaotic here, so I'm behind on at least a dozen projects. I'm not sure why I'm on a forum right now.....