I have a mix of old (fixed 600MHz) and new (autotune) S9s.

Outside peak temps are in the 28-30 celsius (83-86 F) here. I was considering AC but with the added power consumption, mining would be unprofitable.

My old S9s are running around 100-105 C (with a LOT of ventilation), the new ones around 82-88 C. A huge difference.

I'll replace the fans (Delta - 4800 RMP) on the old ones with the same fans the new S9s come with (Nidec UltraFlo - 6000 RPM). I'm hoping that it's only the fan and not the firmware, i.e. if I install the new fans, they will run faster with the old firmware.

Does anyone have any experience with this?