My question topic is Android support for dual SIM hardware. More specifically I'd like to find out if it's the Android 2.2 release that added support for real dual SIM and dual GSM support, and to which extend both cards are online or usable as data channel.
A question about Dual SIM Android phone? already came up here, but it didn't investigate the issue completely. And the mentioned mobile (Tiger G3) was also most likely incorrectly reported as Android phone. From all pictures I've seen it's a regular chinese MTK/NucleuOS phone.
I want to base my question on the STAR A3000 as hardware example. It's verified that it is really running Android, and dual SIM capabilities seem very plausible:
I'm linking to a search listing and not a shop or review directly to avoid the impression of spamvertizing. It's also a more long-lived link that way. But foremost I want to highlight that there are two hardware versions. The original A3000 runs Android 2.1 and offers no dual SIM capabilities. All newer listings advertise both Android 2.2 and dual SIM support.
The trouble with chinese mobiles and resellers is that not all details are super reliable. You'll have to cross check multiple sources, and better assume the lowest common denominator. In the above shop search some Android 2.2 dual sim A3000s are for example still depicted with the original hardware version. I've seen a few images (and there's a youtube video) with the dual sim slots, so I presume this verified. There's also a rumor (on dealextreme) that both hardware versions are identical and there's just a black cover above the second sim slot for the first version (looks plausible from pictures). So that's why I assume that Android 2.1 didn't support such features, and the Android 2.2 kernel maybe introduced it.
The hardware in this phone most likely supports not only dual SIM, but dual GSM. This means that both SIM cards are connected the whole time, to two different networks. All previous MTK chips and mobiles support that.
However I've seen one picture of the A3000 Android 2.2.1 version which shows a configuration screen with an option along the lines "[x] Select SIM card at bootup". This would suggest that it's not a real dual-GSM setup, but just dual-SIM - which only allows switching. Yet all the listings from my first link suggest that the phone and Android is "dual sim dual standby". So I'm confused.
Back to the question: Did Android 2.2 introduce proper support for dual-GSM? I know none of the big brand vendors supports anything like that, so it must be a fringe feature, maybe not even in the OHA documentation. Any chance something like this was mentioned in some sort of release notes? (Really I have no clue, no Android phone yet, still gauging.)
My main interest is keeping my main phone number, and using a secondary SIM and contract for data connnections preferrably. Or the other way round.
Another note. I know there was also the General Mobile DSTL1 once, which was the first (and for a long time only) Android 1.5/1.6 phone to advertise dual-SIM. I don't know to which extend it supported real dual-GSM functionality. But it's interesting that old Android versions allowed it. So I'll extend my question into why no Android 2.0 and 2.1 phones with dual-sim existed. Did the feature possibly come and go twice in Androids lifetime?