I'm happy that I found this post and I appreciate all the info that everyone posted. It helped me to find a solution to my problem with my iMac overheating. I have a couple of things to add - which I hope proves to be helpful to some, in return - from my recent experiences with four fan-control/monitoring programs that I tried (note: the images below are from the developers' websites):
smcFanControl http://www.eidac.de/?cat=40
- Control speeds for: ODD (Optical Drive), HDD (Hard Drive), CPU fans.
- RPM (min/max): ODD (1500/3300), HDD (1500/5500), CPU (940/3400)
- Temperature Threshold settings: none.
- Cool feature: monitoring of Temperature & Fan Speed for one of the three fans in menubar (select corresponding radio button in Preferences).
However, for my iMac, smcFanControl only controlled the CPU fan; I set all three fans to maximum speeds and I could hear them ramp up, then the ODD and HDD fans returned to minimum speeds, while CPU fan remained at whatever speed I selected. Tried both v.2.3 and v.2.4 (released 21AUG12). Contacted developer - no response.
Fan Control 1.2 http://www.lobotomo.com/products/FanControl/index.html (for MacBook, not iMac)
Installs to System Preferences (asks to quit System Preferences before launching program - OK)
- Control speeds for: Left & Right fans.
- Set Base Speeds of both Left & Right fans via one slider.
- Temperature Threshold settings: yes.
Installed this without realizing that it was for MacBook, not iMac. Maximum base speed for fans was ~3400 RPMs each.
For my iMac: Left fan = Optical Drive, Right fan = Hard Drive.
iMac Fan Control 1.2 http://www.derman.com/iMac-Fan-Control
Installs to System Preferences (asks to quit System Preferences before launching program - OK)
- Control speeds for: CPU, HD (Hard Drive), DVD (Optical Drive) fans individually via sliders.
- RPM (min/max): CPU (1200/3500), HD (1200/5500), DVD (1000/4600)
- Temperature Threshold settings: yes.
- Shows Desired / Current Fan Speeds
- Shows Current Temperatures: CPU Heatsink, Internal HD-?, Internal DVD, GPU Heatsink
Program seems to work well (mostly) with my iMac for manually setting the fan speeds, however, today the temperatures went above the minimum threshold settings and the fans did not adjust automatically. Will continue to monitor temperatures and response from program re: fan speeds.
Noticed that maximum speed for the Optical Drive differs between programs:
- iMac Fan Control 1.2: 4600 RPM
- smcFanControl: 3300 RPM
--------- Anyone know what the actual maximum speed for an iMac Optical Drive ought to be? ---------
iStat Pro http://www.islayer.com/apps/istatpro/
Installs to Dashboard.
- Shows temperatures of seven internal points (plus ambient temperature).
- Shows current speeds of fans: Optical Drive, Hard Drive, CPU Fan.
- Shows other cool info about computer (however, none relating to this post).
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iMac i7, OS X Lion 10.7.4