Oh dear. Alright, that's what I was afraid of. I'll look into this more when I have more time but if there's somewhere to grab 5v or 12v from the power supply it might be viable to build an i2c dummy out of an arduino and plug that into the fan headers to fake the switch out. I was hoping it'd be simpler.
It's even worse. The fans in the power supplies are controlled by the switch over i2c as well. If you take apart one of the power supplies (and I did), the fan/power led of the PSU connects to a header inside the PSU. If you remove this wire, the PSU won't turn on...
If you replace the fan IN the PSU with a slower one, the PSU will turn on, but the switch won't boot...'cause..well Brocade said FU when it came to silencing this switch.
That said, in all fairness, the 6610 is 1U switch with almost o.5
tbps of switching bandwidth. That's a lot. The 6610 does get seriously hot, and probably needs these screamers, unless they change the chassis design. After letting the switch run for a few hours, open it up, and you can barely touch the heatsinks for more than a few seconds. They are that hot and that's WITH the screamers. If you even manage to replace the fans with something slower, there's a better than even chance, you'll cook the switch.
I went a slightly different route to silence mine. After realizing I can't change the fans, can't remove them, can't slow them down...well..it's all about airflow and temps, so give the switch more airflow and lower the temps WITH all stock fans. That will make the switch happy, and it'll slow down the fans internally.
So...I cut apart the top cover to mount THREE 120mm fans pretty much covering the front (or back, depending on how you look at it) 3rd of the width. These are nothing special (Yate Loon fans I had lying around) and standard 3 pin 12v fans. Now came the question of how to power them from the switch.
The PSU I had hacked earlier...hacked it even more and soldered wires internally on the big connector (that mates to the switch) to get 12v and GND out. Then routed these two wires carefully out the back of the PSU (next to the power LED), so that I can connect them to the fan header for the 3 fans.
It's pretty "hacky", but I had to get the noise down, my home office is about 10ft from where the rack is and even with a wall in between, in stock configuration, I could hear it...a lot...even on the first floor.