OWC now has a cable with heat sensor that is designed to take care of this problem.
It works with iMac because the Mac system and hardware doesn't know that it isn't an Apple drive. OS updates will not affect this setup. I purchased my cable and drive adapter for a 27" mid 2011 iMac. I wanted to replace my standard internal HD with an SSD.
I have an e-SATA to lightning drive bay that will hold both 2.5 " and 3.5 " drives i use for backups and storage. I inserted the new SSD into the dock and formatted it using disc utility. I then used Carbon Copy Cloner.
I then rebooted iMac to the SSD to make shure it was a successful install. I booted up without any problem. Really darn fast load up and apps just cruise. Then i shut off iMac and begin the drive switch.
I watched their install video 2 times then replaced drives as instructed. No problem with the install process. Cable hooked up and sensor placed on the SSD. Reassembled and fired that puppy up and it worked. No worry about speeding fans or other controlling software. No fear of Apple updates messing with it.
This new cable for this is sold only by OWC as they have the sole rights to this cable and they make it themselves. The drive adapter is $35 which you need no matter what and their propritary cable $15.
Worth every darn cent!
Runs at normal speed. The best thing i ever did to this iMac. I have placed SSD in 12 Mackbook Pro's and 7 IMac's and all have worked just great.