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Mooney, Vincent John, III

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Pareto Points in SRAM Design Using the Sleepy Stack Approach

2005 , Park, Jun Cheol , Mooney, Vincent John, III

Leakage power consumption of current CMOS technology is already a great challenge. ITRS projects that leakage power consumption may come to dominate total chip power consumption as the technology feature size shrinks. Leakage is a serious problem particularly for SRAM which occupies large transistor count in most state-of-the-art chip designs. We propose a novel ultra-low leakage SRAM design which we call "sleepy stack SRAM." Unlike many other previous approaches, sleepy stack SRAM can retain logic state during sleep mode, which is crucial for a memory element. Compared to the best alternative we could find, a 6T SRAM cell with high-V[subscript th] transistors, the sleepy stack SRAM cell with 1.5xV[subscript th] at 110-degree C achieves more than 5X leakage power reduction at a cost of 31% delay increase and 113% area increase. Alternatively, by widening wordline pass transistors, the sleepy stack SRAM cell can match the delay of the high-V[subscript th] 6T SRAM and still achieve 2.5X leakage power reduction at a cost of a 139% area penalty.

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Cache-Related Timing Analysis for Multi-tasking Real-Time Systems with Nested Preemptions

2004 , Tan, Yudong , Mooney, Vincent John, III

In this paper, we propose an approach to estimate the Worst Case Response Time (WCRT) of each task in a preemptive multi-tasking single-processor real-time system utilizing an L1 cache. The approach combines inter-task cache eviction analysis and intra-task cache access analysis to estimate the number of cache lines that can possibly be evicted by the preempting task and also be accessed again by the preempted task after preemptions (thus requiring the preempted task to reload the cache line(s)). This cache reload delay caused by preempting task(s) is then incorporated into WCRT analysis. Two sets of applications are used to test our approach. Each set of applications contains three tasks. The experimental results show that our approach can tighten the WCRT estimate by up to 32% (1.4X) over prior state-of-the-art.

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Golay and Wavelet Error Control Codes in VLSI

2003 , Balasundaram, Arunkumar , Pereira, Angelo W. D. , Park, Jun Cheol , Mooney, Vincent John, III

This technical report describes AGNI (meaning Fire in Sanskrit) – a VLSI chip to implement error control codes. The chip was initially conceived and designed as part of a Georgia Tech Cutting Edge Research Grant. However, this chip implementation of error control codes has been undertaken as a part of the ECE 6130 course taught in Spring 2002 by Dr. John Uyemura, Professor, Department of Electrical and Computer Engineering, Georgia Institute of Technology. Two coders have been implemented: a (12, 6, 4) wavelet encoder/decoder and a (24, 12, 8) golay encoder/decoder, where the (N, M, d) nomenclature stands for (N=encoded length, M=message length, d=hamming distance). These codes have a correctable limit of one bit error and three bit errors, respectively. The following section presents the encoding/decoding functionality of the chip in more detail. This project could potentially feed a future project to incorporate the chip into a System-ona- Package (SoP). It is expected that the chip would function as a high-speed error encoder/decoder for Radio Frequency (RF) applications.

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Timing Analysis for Preemptive Multi-tasking Real-Time Systems with Caches

2004 , Tan, Yudong , Mooney, Vincent John, III

In this paper, we propose an approach to estimate the Worst Case Response Time (WCRT) of each task in a preemptive multi-tasking single-processor real-time system with an L1 cache. The approach combines inter-task cache eviction analysis and intra-task cache access analysis to estimate the number of cache lines that can possibly be evicted by the preempting task and also be accessed again by the preempted task after preemptions (thus requiring the preempted task to reload the cache line(s)). This cache reload delay caused by preempting tasks is then incorporated into WCRT analysis. Two sets of applications are used to test our approach. Each set of applications contains three tasks. The experimental results show that our approach can tighten the WCRT estimate by 38% (1.6X) to 56% (2.3X) over prior state-of-the-art.

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Some Layouts Using the Sleepy Stack Approach

2004 , Pfeiffenberger, Philipp , Park, Jun Cheol , Mooney, Vincent John, III

This technical report elaborates on the methodology and findings presented in “Sleepy Stack Reduction of Leakage Power” by J.C. Park, V. J. Mooney III and P. Pfeiffenberger [1]. The scope of this report includes test procedures and data on delay, dynamic and static power for all considered approaches and implementations as well as schematics and layouts for all considered approaches and implementations.

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Loss-Tolerant and Secure Embedded Computing via Inscrutable Instruction-Set Architectures (I²SA)

2004 , Mooney, Vincent John, III , Palem, Krishna V. , Wunderlich, Richard B.

In short, we examine secure computing where a microprocessor reads, writes and executes operations ideally in an inscrutable domain. The goal is to provide methods and implementations for computation where data never leave the inscrutable domain in which they reside; the intended effect is twofold. The first intended effect is that any transmissions between computing media using our approach would be unbreakable in any reasonable amount of time; i.e., intercepted instructions and/or data would be meaningless to the unauthorized interceptor. The second intended effect is that, as a result of embedded computing platforms realized using inscrutable computing elements, any loss of equipment utilizing such computing hardware would not be very meaningful to the recoverer: we refer to this as loss tolerance.

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An O(NIN(M,N)) Parallel Deadlock Detection Algorithm

2003 , Lee, Jaehwan , Mooney, Vincent John, III

This paper presents a novel Parallel Deadlock Detection Algorithm (PDDA) and its hardware implementation, Deadlock Detection Unit (DDU). PDDA uses simple boolean representations of request, grant and no activity so that the hardware implementation of PDDA becomes easier and operates faster. We prove that the DDU has a worst-case run-time of 2 x min(m, n) - O(min(m,n)), where m is the number of resources and n is the number of processes. Previous algorithms in software, by contrast, have O(m x n) run-time complexity. We also prove the correctness of PDDA and the DDU. The DDU reduces deadlock detection time by 99.9%, (i.e., 1000X) or more compared to software implementations of deadlock detection algorithms. An experiment involving a practical situation that employs the DDU showed that the time measured from application initialization to deadlock detection was reduced by 46% compared to detecting deadlock in software.

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