Originally Posted by NormM
I got the late 2010 Air soon after it came out, and I don't have Power Nap under Mountain Lion. The SMC update for the 2011 Air isn't compatible, and I don't see any other update available. I suspect something changed after my Air debuted, so perhaps most 2010 Air's support Power Nap, but not mine :(
[[Update: there was a Mountain Lion developer's beta for the late model 2010 Air SMC that enabled Power Nap. Those that have it on those machines may have been developers. There's a thread about this on MacRumors. Don't try to install the beta SMC firmware packages discussed there on anything other than a late 2010 Air!! They don't have the usual user-friendly compatibility checks!]]
Bingo! I have a dev installation of 10.8 on my late 2010 11" MacBook Air. That explains why I have the Power Nap feature (and shouldn't).
The downside is that my SMC was flashed/updated to the current version for mid 2011 through 2012 models. I say "downside" because this has caused my MBA to suffer from severe battery drain, even after disabling Power Nap. Where I generally enjoyed 5 to 6 hours of use I now am lucky to get 3. Unfortunately my SMC version cannot be easily flashed back to what it should be, and I didn't renew my dev license so I'm either going to have to wait for v10.8.2 which includes a modification to Power Nap...and hopefully the SMC...or visit my Apple store to see if they can put things back to normal.
It's clear that, at least for my model of MBA, the SMC version that supports Power Nap is not currently viable.
FWIW as Norm mentions, there is a thread on another forum that links to a download package that allows Power Nap to be activated on non-supported machines, specifically late 2010 11" and 13" MacBook Airs. I'd highly caution against doing that based on the battery issues many of us are encountering due to the SMC change. More here.
Edited by richsadams - 9/6/12 at 11:06am