An X-tolerant multiple-input signature register (MISR) compaction methodology that compacts output streams containing unknown (X) values, called X-canceling, is an alternative to masking X values (i.e., X-masking). A number of control bits that is linear in the number of X's to be canceled are required to perform the X-canceling operation for existing X-canceling approaches. This paper proposes a new X-canceling method significantly reducing the number of control bits for X-canceling. We exploit the fact that 1) unknown values tend to be highly correlated in the scan cells (i.e., X's tend to be generated in certain portions of design) and 2) fault effects can typically be observed in a multiplicity of scan cells. Instead of custom generating the control bits to cancel out only the X's in one MISR signature, the proposed approach finds a general superset solution which can cancel out the X's for many MISR signatures without losing fault coverage. This allows the same control bits to be reused many times thereby significantly improving the amount of compression that can be obtained. Architectures for implementing superset X-canceling are described along with experimental results.

Adaptive-granularity memory architectures have been considered mainly because of main memory bottleneck and power efficiency. Meanwhile, highly reliable protection schemes are getting popular especially in large computing systems. Unfortunately, conventional ECC mechanisms including Chipkill require a large number of symbols to guarantee strong protection with acceptable overhead. We propose a novel memory protection scheme called CLEAN (Chipkill-LEvel reliable and Access granularity Negotiable), which enables us to balance the contradicting demands of fine-grained (FG) access and strong & efficient ECC. To close a potentially significant detection coverage gap due to CLEAN's detection mechanism coupled with permanent faults, we design a simple mechanism access granularity enforcement. By enforcing coarse-grained (CG) access, we can get only the advantage of higher protection comparable to Chipkill instead of achieving the adaptive access granularity together. CLEAN showed Chipkill level reliability as well as improvement in performance, system and memory power efficiency by up to 11.8%, 10.8% and 64.9% with mixes of SPEC2006 benchmarks.

This paper describes and evaluates a scalable and efficient resilience scheme based on the concept of containment domains. Containment domains are a programming construct that enable applications to express resilience needs and to interact with the system to tune and specialize error detection, state preservation and restoration, and recovery schemes. Containment domains have weak transactional semantics and are nested to take advantage of the machine and application hierarchies and to enable hierarchical state preservation, restoration, and recovery. We evaluate the scalability and efficiency of containment domains using generalized trace-driven simulation and analytical analysis and show that containment domains are superior to both checkpoint restart and redundant execution approaches.

An alternative to masking unknown (X) values before the compactor (i.e., X-masking) is to capture X's in the MISR and cancel them out after compaction (i.e., X-canceling). Existing X-canceling methodologies require a number of control bits to perform the X-canceling that is linear in the number of X's to be canceled. This paper describes a new methodology for X-canceling which can exploit the fact that the scan cells in which X's are captured tend to be highly correlated in order to significantly reduce the number of control bits required for X-canceling. X's tend to be generated in certain portions of the design, and hence certain scan cells capture X's with much higher frequency than other scan cells. Instead of custom generating the control bits to cancel out only the X's in one MISR signature, the proposed approach finds a general superset solution which can cancel out the X's for many MISR signatures. This allows the same control bits to be reused many times thereby significantly improving the amount of compression that can be obtained. Architectures for implementing superset X-canceling are described along with experimental results.