Sleepy iMac – reset SMC

Q. My iMac wouldn’t turn on this morning. I checked all the connections, and they were good. I then unplugged it from the back and plugged it back in. After that it started up. Is this a normal thing? Is it a potential problem?

A. I wouldn’t call that situation “normal” but I have seen it before. By unplugging your iMac’s power cord, you have reset the SMC chip which controls power settings. All Macs these days have an System Management Controller (SMC) which manages all of the power functions of your computer. These include power and thermal monitoring, sleeping and the battery. It also controls the fans, the Sudden Motion Sensor in laptops and the power switch.

We’ve also heard from MacBook users who have trouble waking their Macs from sleep. (Closing the lid, waiting until the LED pulses and then re-opening the lid often works.) The method for resetting the SMC on laptops vary – you can check out how to reset your Mac model at The fact that Apple put in an SMC chip means that it is “normal” and that it could lead to potential issues.

Whether it’s a potential problem is also good question… power is always a potential problem especially in older homes. The best advice I can give is that all of your desktop computers should be on a “smart” UPS – which is an uninterruptible power supply with a line conditioner. It is basically like a car battery with a line conditioner to absorb spikes in voltage/amps. They range in price from $100 to $2000 depending on the protection you need.

An inexpensive model for the iMac (BackUPS 350VA) would be around $70. One that could cover three Macs (BackUPS 1200VA) would be around $200. I have the latter in my office for my Mac and Internet modem, router and Time Capsule. That would give you between 10 to 15 minutes of runtime if the power went out and generally provide “clean” power to the equipment. Models for larger Macs and servers which would give about an hour of running time would cost about $1500 and up.

Leave a Reply

This site uses Akismet to reduce spam. Learn how your comment data is processed.