Ultra-low power designs are increasingly exploiting the sub-threshold region of operation of CMOS circuits. In order to ensure correct functionality in a design, it is necessary to guarantee signal integrity. We evaluate crosstalk in an industrial microprocessor core designed in 65nm Bulk CMOS technology as the operating voltage is reduced from nominal to sub-threshold. We partition the problem into categories dictated by crosstalk analysis: crosstalk induction, crosstalk propagation and failure criterion (noise rejection curve of msff). We develop testbench circuits to study these analysis components individually. We also selected 2500 noise sensitive interconnects from the industrial microprocessor design and simulated them for crosstalk with varying operating voltages. We observe that although crosstalk injection increases in sub-threshold operation, the propagation does not, resulting in overall less crosstalk sensitive design.