iMac, Windows 7, and fan speeds
August 7, 2013 10:19 PM   Subscribe

I have a 2008 24" iMac that I've used BootCamp to get Windows 7 running. Issue: the fans never come on.

This is documented around the web, and I use (and have used in the past, when I had this running XP) SMC Fan Control. My procedure is:

1) Turn SMC Fan Control on in OSX
2) Reboot into Windows (holding down Option on boot)
3) Now the fans will stay running until shutdown

If I don't do this, the top of the computer is physically painful to touch from the heat, which I figure.. can't possibly be good for anything. So I have a few questions:

1) Is this something to worry about?
1a) This is my only computer, it's a long time out of AppleCare, and I'd rather not have to buy a new computer right now

2) IF this is something I should be messing with, is there some better way to handle this?
2a) What fan speeds should I be aiming for? I can't set it to be temperature-based, it has to be a set RPM
posted by curious nu to Computers & Internet (4 answers total) 1 user marked this as a favorite
This is a huge issue to worry about, if the fans never come on your iMac will cook itself and fail catastrophically. You should stop using it this way immediately. If you need Windows on your Mac for free, use Virtualbox to run the boot camp partition as a virtual machine "guest" OS inside OS 10.6/10.7/10.8.
posted by thewalrus at 10:24 PM on August 7, 2013

SMC is probably the best way to handle this. And the reason the settings are not temperature-based, well, that's addressed by the developer. What SMC does is set a minimum fan speed. This approach is less intrusive, and it safeguards against temperature misreads and doesn't require a daemon process running in the background.

If you want a reference point, one application I use fires up my MBP to around 210°F.

The following is a matter of opinion, but if you're booting into Windows and fan control is lost but can be set via SMC - which frankly, is a little surprising - I'd max out the fans, I don't see a problem with that. It's not like SMC lets you set the fan speed to some insane number; you're within Apple's limits. Something in the high 5,000's.
posted by phaedon at 10:40 PM on August 7, 2013

Best answer: 1) Is this something to worry about?

Yes, but as anecdata you should never ever need to set the fans above lie, 1500rpm. If i wanted to be 100% safe and sure it would never overheat i'd set them to like, 1800 or 2000. The fans on mine never exceed 1500-1600 on my 2007, hotter because of an older less efficient cpu, smaller(20in, more stuff crammed in to less space) iMac.

I've had this heat issue with several macs of various earlier intel revisions. 2008 macbooks, 2009 macbook pros, 2007 macbook pros, 2006 imacs... There's some weird entirely software controlled voodoo going on with apples fans on a lot of theri systems. It's a well documented issue online, and i don't understand why they don't have some deep firmware like a lot of other high quality machines(dells pro stuff like the better latitudes of old and the precisions, thinkpads, etc) where a bios level thing will go OH CRAP THIS SHITS OVERHEATING and flip the fans on to either 90% or full blast until the temp drops below some predefined threshold you don't get to set.

The heat will kill your motherboard. Absolutely, 100%. It won't even take very long. You might also blow out your video card(which while replaceable as a seperate unit unlike later imacs and many similar systems, is an EXTREMELY overpriced part. Like $300 on a machine that's only really worth 450 or so anymore). Any damage this could cause to the machine would end up being something like 80% if not near the full purchase price of another comparable machine on the used market.

Oh, and i'd never set the fans to 100%. I've blown out fans on several small/thin machines doing that type of thing. I have seen macbook pro fans fail, and the fans in my imac sound a little erm... gravely after all these years and a few blast outs with an air compressor. OSX will never run the fans at 100%, or even it seems, 75% and i've never had the cpu temp go above about 60c even when left on for hours rendering 1080p video in premiere... with the cpu fan at 1600rpm, the other main one at 1500, and that "optical drive" one at 1000.

Just set the fans to like 2000rpm in smc fan control and rock out.

The big * here though is what do you need to do in windows? Unless it's like, gaming just use parallels or virtualbox or something. The fan control will work perfectly and honestly it runs plenty fast. I never really find myself going "Ugh, this VM shit is lame" unless i'm trying to game.

On preview, i just remembered screwing around with this. I forget if it worked, but have you tried this? I feel like it worked on some of the macs i've had, and not on others. I'd just generally google "fan control windows imac" and try every single thing you see suggested. Something will likely work, i only remember that stuff not working on what was at the time a very new and not very hacked on yet mac, my 2010 macbook pro( 2010)
posted by emptythought at 1:01 AM on August 8, 2013

Best answer: You can also try this, which works fine for me on a 27" 2010 iMac, although it gives some strange names to the fans. I run them at 2000 rpm while gaming in Win7 and it keeps things warm but not hot.
posted by McCoy Pauley at 4:23 AM on August 8, 2013 [1 favorite]

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