Irregularly Shaped Voltage Islands Generation with Hazard and Heal Strategy

Zhen Meng,  Song Chen,  Lu Huang
Department of Electronic Science and Technology, USTC, China


Irregular Shaped Voltage Islands (ISVI) can achieve much better power savings in multiple supply voltage (MSV) technology. This paper proposes a simulated annealing (SA) based floorplanning method with ISVI generation using a Hazard and Heal strategy. In each perturbation of SA, a randomly chosen block is removed from floorplan and then inserted back to a proper position, to join certain voltage island. The solution space for every iteration is O(n2kvi), where n is block number and kvi is voltage island number. Every position with voltage island assignment is evaluated by a linear combination of chip area, wire length, power and voltage island cost. To avoid timing-consuming evaluation of O(n2kvi) possibilities, we propose a fast Hazard method to construct ISVI by skipping lots of distant voltage island candidates while occasionally accepting seldom-emerged illegal (non-contiguous) candidates. To resolve the seldom-emerged non-contiguous voltage islands, a detailed Heal method is applied in each temperature. Experimental results show the proposed method is effective and efficient compared with the latest works.