Does push-pull really matter in a system without much flow constriction? My understanding was that helped maintain airflow in an environment with lots of obstruction, like close-packed heatsink fins, but the R909 is pretty open.
I'm not sure about that myself.
Earlier today I tried 550MHz with the NF-A8 installed and the stock fan placed in front of it, it seemed to make no difference. I remember someone trying this in a different application and they had the same results. Somehow, it was effective on the Futurebit Apollo, though. However that device was exhausting up top, with the fan pulling air through a pretty dense heatsink. So by the time it reached the top, the airspeed was quite slow.
After those experiments, I placed the stock fan in the back, covering roughly half of the back area and set the miner to 700MHz. (I know; not very scientific. I should stick to 550 now, for further experiments).
Anyhow, I'm now seeing 2.6Th/s, something I have never experienced with this miner before.
0: GSF 10070017: BM1397:06+ 700.00MHz T:700 P:694 (3:2) | 91.6% WU: 93% | 2.507T / 2.613Th/s WU:36505.2/m
Let's see if it can keep this up. So far, that's a 4:30h average. I'm also interested to see if the hashrate drops off over the next 24h or if this double fan setup keeps it above 2.5.