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Today, designing reliable superscalar microprocessors is more complex and challenging than it has always been. Increasing current densities over interconnecting wires, whose dimensions are continuously scaling down, has been an important research problem. Performance and power efficiency concerns also lead to more complex structures. The complexity and the wire densities of the blocks in smaller areas make them more prone to failures and malfunctions caused by the "electromigration" problem. Most contemporary processors employ wide pipelines that are able to execute multiple instructions each cycle. Because of some limiting factors such as the dependencies and input/output latencies, pipelines are rarely used up to their full capacity, which causes some ports to be used more and worn out earlier. This paper proposes a method to help preventing chips against the corruptive effect of electromigration by distributing the utilization evenly between ports. Furthermore, in data holding structures like register files, bit level inactivity is exploited to provide further reliability improvements. This is accomplished by changing the flux density on wires through exchanging the positions of significant bits of values and changing the widths of bit line wires according to their level of usage.

Soft errors caused by cosmic rays or alpha particles emitted from the packaging material around the chips are becoming an increasingly important challenge in reliable microprocessor design. Transistor density, and die size trends show that soft errors will gain even more importance in the future. Due to their significant overheads, most redundancy schemes are employed where the penalty incurred can be hidden in the pipeline. Most contemporary processors employ a large physical register file to hold the produced results which may reside there for a long time. The register file is a critical element of a microprocessor and is needed to be protected against soft errors. In this paper we propose an SRAM bitcell design with ability to hold a redundant copy of the data and compare the copies with built-in comparators to detect a possible mismatch. Our experimental results show that the proposed design has 34% area, 7.9% power 2% delay overheads which are further reducible and can protect the register file against Silent Data Corruption (SDC).