The gyro part ADXRS644 is listed in this selection table: http://www.analog.com/static/imported-files/selection_tables/MEMS_Inertial_Sensors_Selection_Tables.pdf
However, no other information can be found on it, and it does not appear to exist outside of this PDF document. Is this a future part? Error?
The table specs on it look great... nearly identical to the ADXRS646, but with in-run bias of just 9deg/hr.