Sooooo... I decided that 50% speed on these G8 fans is a *bit* much (55db-ish), so I decided to build a manual fan controller.
I purchased this one from Amazon (4-pin PWM with a manual knob):
I stripped it of it's 6 & 4 pin connectors and the 3 electrolytic capacitors (the big green ones) to make it as short as possible leaving only the circuitry for the PWM controller IC in place.
I then cut all 4 green wires in the G8's fan wire harness (PWM control wires for the fans), soldered them together into a single wire, and soldered that wire to the PWM output pin of one of the 4-pin connectors on the fan controller.
I then tapped into the G8's fan harness again for 12v power/ground and soldered those wires to the same 4-pin connector (from above) on the stripped fan controller (I didn't need to solder to the 6-pin connector because this fan controller shares a common 12v power plane and ground plane across the 4/6-pin connectors).
Finally, I wrapped the fan controller with electrical tape *and* heatshrink, tucked the wrapped fan controller into the space behind the top drives and mounted the knob to the bracket behind the fans (fan in front of the knob still slides in with about 2mm of clearance to spare).
Result:
- G8 fans still use 12v power/ground feeds directly from the server (not from the fan controller)
- G8 fans still report their fan speed to the G8 motherboard (not visible in iLO due to G9 BIOS cross-flash, but *is* visible in applications that can read motherboard sensors)
- Fan controller taps into the above 12v power/ground feeds to power itself (in this case *just* the PWM IC), and then feeds it's PWM output signal directly to the G8's 4 fans
Upside:
- I have full (manual) control of the G8's fans in a hidden (but easily accessible) way.
Downside:
- Due to choosing to use a manual fan controller, the fans still don't ramp up with load (this could be easily resolved with a temperature-based fan controller with a probe, but I prefer finer control).
Based on my average server load (4x E7-8891 v4, 256GB DDR3, 4x GTX 1080 GPUs, 10x 2.5" 7200RPM SAS HDDs and 4x 1TB NVMe SSDs running 12 virtual machines 24/7) I can run these fans at less than 20% of their full speed and still keep the server cool (CPUs around 50C in a concrete room with no A/C with average ambient temperature of 70-80F).