Today’s announcement of the Nokia Lumia 610 ushers in a new class of lower cost devices. To support these new devices, Windows Phone Tango will bring changes that allow for the decreased specs that are now supported. Developers preparing their apps for this new market can start testing their applications today with the newly released technical preview of the SDK update. This provides access to a 256MB emulator that will allow you to preview performance of apps on lower memory devices.
A final version of the SDK will be available next month.
Source: Windows Phone Blog