It took considerably longer than I expected, but I've finally been able to test the WWAN functionality several weeks after receiving my 3G-enabled UMID mbook M1 (32GB SSD, 1.33GHz Intel Atom, 512MB RAM, Windows XP). Whether the 3G module, identified in the Device Manager as the CMO6007, was compatible with the 3G bands used in the US has always been anyone's guess, so the first thing I did after getting the system to work properly was grab my AT&T SIM card.
Why no one has been able to confirm exactly which bands are supported is beyond me, but I suppose there's a reason the 3G UMID isn't really being promoted here in the states.
As far as I can tell, it doesn't work. Not with AT&T's 850MHz/1900MHz 3G network, anyway. I suppose there's a slim chance that a T-Mobile SIM could work, but I have my doubts.
I know for a fact that the functionality works perfectly in Hong Kong and Australia, though I've heard from a few users that APN and band settings needed to be customized first. I assume it's because my SIM isn't recognized, but I'm actually not able to access any of the menu options shown above to fiddle with settings. Clicking on any of the options (SIM Setting, Profile Setting, etc.) results in a highlighted choice that launches nothing. I've seen what's supposed to happen and "nothing" is not it.
My SIM works just fine in other devices, so I know it isn't defective.
The bottom line is simply this: the 3G UMID mbook M1 that can be imported into the US is not compatible with AT&T cards. I still haven't received a straight answer about whether anyone else in the US has been able to get the 3G functionality to work (and I've pretty much given up on ever getting a definitive list of supported bands), but based on my own tests and experiences, I wouldn't recommend that anyone in the states spend the extra money to get the black M1 with built-in 3G.
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