Fan toggling on off on off on off relentlessly...I got a Dell Precision M6700 I got at the end of last year and it has come dangerously close to becoming an expensive projectile several times. There is something REALLY wrong with the temperature / fan control. Tools like SpeedFan don't recognize the fans in many Dell machines like this one (probably because of the "special" Dell BIOS that isn't worth the time for the developers to support), so they're of no use to override the boneheaded Dell fan control logic. The BIOS keeps turning the fans off, and allowing the temperature to rise a few degrees, then turning the fans on full blast until the temperature drops a few degrees. Watching the main CPU temp and the GPU temp graph out a consistent (even if jagged) sine-wave is proof that someone just didn't make much of an effort when they wrote the fan control software. The same moron engineer would probably also think it is a good idea to paint the walls in a dining room with glow-in-the-dark paint and turn on a blindingly bright light for a short time every few minutes.
After many futile web searches, I stumbled over an older conversation about a different Dell laptop model (XPS) and a different graphics card (Nvidia) that was doing the same stupid fan-on, fan-off thing (apologies to Mr. Miyagi). The conclusion there was that the Video card drivers were to blame. That would have been great for me if I had the same type of video card, but my M6700 has an ATI / AMD FirePro graphics card, with totally different drivers. I decided it was worth a shot updating the graphics drivers anyway.
After updating to a new version of the Catalyst Pro Control Center from AMD (formerly ATI), and re-packaged by Dell for their own "special" "made for Dell" version of the graphics card, a new option (at least one I hadn't noticed before) showed up in the "Power" settings. A feature called "PowerPlay" had previously plugged itself into the Windows power management options. PowerPlay allowed one of two settings, "Maximize Performance" or "Maximize Battery Life." One of those two options could be selected as active when "Plugged In" and one of the same two options could be selected as active when running on the battery. It makes no sense to name something "Maximize Battery Life" as an option that is available when "Plugged In" but that's beside the point. The "new" option available in the Catalyst Pro Control Center was a checkbox labeled "Enable PowerPlay." Unchecking that box to completely disable "PowerPlay", and clicking the "Apply" button caused the GPU temperature to drop and stabilize around 50 degrees C. At first, this seemed to resolve the on off on off on off nonsense, but after a little while it was back to the same on/off/on/off/on/off behavior.
I wish I could say this issue was resolved, but so far, the toggling fan on the m6700 seems to be be a fact of life. This will probably be the very last Dell computer I ever bother to buy. Sorry Dell... if you can't get something as simple as fan-speed right, I can't trust you with much else.
I'm hoping maybe this is one piece of the puzzle and that someone else may have figured out what else is contributing to the bizarre (lack of) fan control on the M6700. Please leave a comment if you know of something else that helps with this issue.