Instruction-based self-test for delay faults maximizing operating temperature

Abstract

In today's technology, reliability is one of the major challenges. Process variations and increasing power density in advanced technology nodes make the condition even worse. Process variations during manufacturing induce delay variations and such variations may manifest into faults at the higher temperature during operation. Delay faults at higher functional temperature is a critical factor for the reliability of a system. Current DFT-based methods do not handle this properly. In this paper, we propose an instruction based self-test (IBST) technique to elevate the temperature of a chip near to functional temperature and test it for delay faults at that temperature. In the first step, integer linear programming (ILP) is used to find out power hungry instructions. These instructions cause maximum toggling in a unit. In the second step, delay test instructions are combined to create a program for testing functional unit of an out-of-order superscalar processor. Experimentation of the proposed technique is carried out on portable ISA (PISA) based superscalar processor. Higher operating temperature 95°C ± 2°C is achieved and it is maintained while applying delay test.