STT-RAM cells can be considered as an alternative or a hybrid addition to today's SRAM-based cache memories. This is mostly because of their scalability and low leakage power. Moreover, their data storing mechanism (storing the value as resistance) makes them very suitable and applicable for multivalue cache architectures. This feature results in system performance enhancement without any area overhead. On the other hand, the required two-step read/write procedure in multilevel cells results in a non-uniform time access and energy and power overhead on the system. In this paper, we propose a new architecture to dynamically swap data between soft (fast read access) and hard (slow read access) bits in ML cell. Moreover, by reconfiguring cache block size, the proposed architecture can switch between ML and SL modes at runtime. In other words, the swapping method places the hot part of each cache block into soft-bits and the less accessed part into the hard-bits. The SL/ML switching method benefits from the low latency and energy of SL mode and the high storing capacity of ML mode at the same time. Although experimental results show that our proposed method slightly increases the miss rate compared with the conventional ML caches, the performance and energy are improved by 4.9% and 6.5%, respectively. Also, the storage overhead of our method is about 1% that is negligible.

Transistor and interconnect wearout is accelerated with transistor scaling resulting in timing variations and consequently reliability challenges in digital circuits. With the emergence of new issues like Electro-migration these problems are getting more crucial. Age monitoring methods can be used to predict and deal with the aging problem. Selecting appropriate locations for placement of aging monitors is an important issue. In this work we propose a procedure for selection of appropriate internal nodes that expose smaller overheads to the circuit, using correlation between nodes and the shareability amongst them. To select internal nodes, we first prune some nodes based on some attributes and thus provide a near-optimal solution that can effectively get a number of internal nodes and consider the effects of electro-migration as well. We have applied our proposed scheme to several processors and ITC benchmarks and have looked at its effectiveness for these circuits.

In this paper we propose to think out of the box and discuss an approach for universal mitigation of Negative Bias Temperature Instability (NBTI) induced aging untied from the limitations of its modelling. The cost-effective approach exploits a simple property of a randomized design, i.e., the equalized signal probability and switching activity at gate inputs. The techniques considered for structural design randomization involve both the hardware architecture and embedded software layers. Ultimately, the proposed approach aims at extending the reliable lifetime of nanoelectronic systems.

Transistor and interconnect wearout is accelerated with transistor scaling resulting in timing variations and consequently reliability challenges in digital circuits. Age monitoring methods can be used to predict and deal with the aging problem. Selecting appropriate locations for placement of hardware aging monitors is an important issue. In this work we propose a procedure for selection of appropriate internal nodes in combinational clouds between pipeline stages or combinational parts of a sequential circuit to place hardware monitors that can effectively provide aging information of various components of a modern digital system. In order to implement the node selection procedure, we propose an object-oriented model. Object-oriented model of a circuit along with a probabilistic and logical simulation engine that we have developed can effectively be used for implementation and also fast evaluation of the proposed node selection mechanism. The proposed object-oriented C+ + models can be integrated into a SystemC RTL model making it possible to perform mixed-level simulation, and integrated evaluation of a complete system. We have applied our proposed scheme to several processors including MIPS, ARM, ALPHA and MiniRISC and have looked at its effectiveness for these processors.

Transistor and interconnect wearout is accelerated with transistor scaling that results in timing variations. Progressive age measurement of a circuit can help a better prevention mechanism for reducing more aging. This requires age monitors that collect progressive age information of the circuit. This paper focuses on monitor structures for implementation of progressive age detection. The monitors are self-adjusting that they adjust themselves to detect progressive changes in the timing of a circuit. Furthermore, the monitors are designed for low hardware overhead, and certainty in reported timing changes.