The current Chassis 1 specs as per April 2011.
The goal is likely to to further reduce the cost of a low-end Windows Phone. While Tom Warren from the Verge claims 512 MB was a requirement the Windows Phone Chassis has always specified 256 MB or more, but presumably OEMs have not found that Windows Phone runs well with those specs. If the Verge is right this situation is likely to change.
While we all know Windows Phone Tango will enable low-end handsets, it is still not clear if it will include features which users with higher end handsets will also find desirable.
Read more of our Windows Phone Tango coverage here.
Thanks Simon for the tip.