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OS X 10.8 "Mountain Lion" Q&A - Updated September 24, 2012

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What is "Power Nap"? Which Macs are compatible with Power Nap? Are there any "hacks" to use Power Nap with incompatible Macs?

Within Apple's official promotional copy, the company explains that Power Nap makes it possible for your Mac to go to sleep and "still get things done."

Specifically, Apple explains that a compatible Mac:

Periodically updates Mail, Contacts, Calendar, Reminders, Notes, Photo Stream, Find My Mac, and Documents in the Cloud. When your Mac is connected to a power source, it downloads software updates and makes backups with Time Machine. While all that updating is going on, the system sounds are silent and no lights or fans come on, so nothing disturbs you. And when your Mac wakes up, it's good to go.

Some may appreciate this automatic convenience, whereas others may prefer to update or sync their Mac with more granular control or at least they themselves be awake and aware of updates. Regardless, for those who appreciate the convenience, the number of systems supported is quite small.

Power Nap Compatible Macs

Apple's original promotional copy noted that these general Macs support Power Nap:

On September 19, 2012, Apple added the Late 2010 MacBook Air models with the 10.8.2 update.

More precisely, these Macs support Power Nap:

Future Apple notebooks with "integrated" SSDs -- which presumably will be all Apple notebooks for the foreseeable future -- also will support Power Nap. No Apple desktops support this feature nor does Apple provide any support for other models.

Identification Help

If you aren't sure whether or not you have a Mac that is compatible with Power Nap, all of these models can be identified by both external and software identifiers.

Specifically, all of these models can be uniquely identified externally by EMC numbers and in software by model identifier:

Notebook Mac EMC Number Model Identifer
Late 2010 11" MacBook Air 2393 MacBookAir3,1
Late 2010 13" MacBook Air 2392 MacBookAir3,2
Mid-2011 11" MacBook Air 2471 MacBookAir4,1
Mid-2011 13" MacBook Air 2469 MacBookAir4,2
Mid-2012 11" MacBook Air 2558 MacBookAir5,1
Mid-2012 13" MacBook Air 2559 MacBookAir5,2
Retina Display MacBook Pro 2512 MacBookPro10,1


EveryMac.com's Ultimate Mac Lookup feature also can uniquely identify each one of these models by their serial numbers.

Originally Supported Models & Hack Possibilities

As first discovered by site sponsor OWC, Apple also announced support for the "Late 2010" MacBook Air models prior to the release of the OS X Mountain Lion, but quietly dropped this support when the OS actually shipped. Apple re-added this functionality on these models with the 10.8.2 update on September 19, 2012.

In initial testing, OWC found that Power Nap worked on the 13-Inch "Late 2010" MacBook Air, but not on the 11-Inch model. After additional testing on multiple 13-Inch "Late 2010" models, OWC concluded that it "seems hit-or-miss for compatibility. With those that it worked for, it did so without any extra changes. For those it didn't work with, it just wasn't enabled. We couldn't find any rhyme or reason to why some worked and some didn't."

As it turns out, it appears that Apple simply dropped inital support for the "Late 2010" MacBook Air precisely because it was so buggy and apparently did not have time to fix it prior to shipping the operating system. When running 10.8.2, it works as originally advertised.

Some extremely adventurous users in the MacRumors Forums originally experimented with "beta" firmware from pre-release versions of OS X Mountain Lion to varying degrees of success to enable Power Nap on the "Late 2010" MacBook Air models prior to the release of 10.8.2 -- and also experimented on other models -- but it is never a good idea to experiment with "beta" or third-party firmware revisions. EveryMac.com strongly recommends that you do not attempt to install pre-release or unofficial firmware revisions.

In basic terms, firmware runs "directly" on the hardware and improper firmware could result in a completely inoperable computer. Theoretically, someone could write a firmware "hack" to enable Power Nap on additional Macs, but it would be a highly skilled hack and it is unlikely to merit the attention. Furthermore, it would be quite risky to trust a firmware hack from an unknown third-party.

As the Power Nap feature is unlikely to be important for most and "beta" firmware and firmware "hacks" are to be avoided, it's definitely best to leave well enough alone.



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