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Author

Sunggu Lee

Other affiliations: University of Michigan, Samsung
Bio: Sunggu Lee is an academic researcher from Pohang University of Science and Technology. The author has contributed to research in topics: Overhead (computing) & Memory management. The author has an hindex of 20, co-authored 101 publications receiving 1251 citations. Previous affiliations of Sunggu Lee include University of Michigan & Samsung.


Papers
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Journal ArticleDOI
TL;DR: The proposed design, even with the additional error recovery module, is more accurate, requires less hardware, and consumes less power than previously proposed 4–2 compressor-based approximate multiplier designs.
Abstract: Approximate multiplication is a common operation used in approximate computing methods for high performance and low power computing. Power-efficient circuits for approximate multiplication can be realized with an approximate 4–2 compressor. This letter presents a novel design that uses a modification of a previous approximate 4–2 compressor design and adds an error recovery module. The proposed design, even with the additional error recovery module, is more accurate, requires less hardware, and consumes less power than previously proposed 4–2 compressor-based approximate multiplier designs.

130 citations

Journal ArticleDOI
TL;DR: The design and implementation of a crypto processor, a special-purpose microprocessor optimized for the execution of cryptography algorithms, which can be used for various security applications such as storage devices, embedded systems, network routers, security gateways using IPSec and SSL protocol, etc.
Abstract: This paper presents the design and implementation of a crypto processor, a special-purpose microprocessor optimized for the execution of cryptography algorithms. This crypto processor can be used for various security applications such as storage devices, embedded systems, network routers, security gateways using IPSec and SSL protocol, etc. The crypto processor consists of a 32-bit RISC processor block and coprocessor blocks dedicated to the AES, KASUMI, SEED, triple-DES private key crypto algorithms and ECC and RSA public key crypto algorithm. The dedicated coprocessor block permits fast execution of encryption, decryption, and key scheduling operations. The 32-bit RISC processor block can be used to execute various crypto algorithms such as Hash and other application programs such as user authentication and IC card interface. The crypto processor has been designed and implemented using an FPGA, and some parts of crypto algorithms has been fabricated as a single VLSI chip using 0.5 /spl mu/m CMOS technology. To test and demonstrate the capabilities of this chip, a custom board providing real-time data security for a data storage device has been developed.

106 citations

Proceedings ArticleDOI
05 Jun 2011
TL;DR: In order to reduce DRAM refresh energy which occupies a significant portion of total memory energy, a runtime-adaptive method of DRAM decay is presented and two methods, DRAM bypass and dirty data keeping, are presented for further reduction in refresh energy and memory access latency.
Abstract: Hybrid main memory consisting of DRAM and non-volatile memory is attractive since the non-volatile memory can give the advantage of low standby power while DRAM provides high performance and better active power. In this work, we address the power management of such a hybrid main memory consisting of DRAM and phase-change RAM (PRAM). In order to reduce DRAM refresh energy which occupies a significant portion of total memory energy, we present a runtime-adaptive method of DRAM decay. In addition, we present two methods, DRAM bypass and dirty data keeping, for further reduction in refresh energy and memory access latency, respectively. The experiments show that by reducing DRAM refreshes, we can obtain 23.5%~94.7% reduction in the energy consumption with negligible performance overhead compared with the conventional DRAM-only main memory.

97 citations

Journal ArticleDOI
TL;DR: This paper critically surveys methods for the automated probabilistic diagnosis of large multiprocessor systems and produces a chart showing the comparative advantages of the various diagnosis algorithms on the basis of several factors important to the probabilism diagnosis.
Abstract: This paper critically surveys methods for the automated probabilistic diagnosis of large multiprocessor systems. In recent years, much of the work on system-level diagnosis has focused on probabilistic methods, which can diagnose intermittently faulty processing nodes and can be applied in general situations on general interconnection networks. The theory behind the probabilistic diagnosis methods is explained, and the various diagnosis algorithms are described in simple terms with the aid of a running example. The diagnosis methods are compared and analyzed, and a chart is produced, showing the comparative advantages of the various diagnosis algorithms on the basis of several factors important to the probabilistic diagnosis.

72 citations

Journal ArticleDOI
TL;DR: The IHC algorithm with the minimum value of /spl eta/ is shown to be optimal in minimizing the execution time of ATA reliable broadcast when used in a dedicated mode (with no other network traffic).
Abstract: All-to-all (ATA) reliable broadcast is the problem of reliably distributing information from every node to every other node in point-to-point interconnection networks. A good solution to this problem is essential for clock synchronization, distributed agreement, etc. We propose a novel solution in which the reliable broadcasts from individual nodes are interleaved in such a manner that no two packets contend for the same link at any given time-this type of method is particularly suited for systems which use virtual cut-through or wormhole routing for fast communication between nodes. Our solution, called the IHC Algorithm, can be used on a large class of regular interconnection networks including regular meshes and hypercubes. By adjusting a parameter /spl eta/ referred to as the interleaving distance, we can flexibly decrease the link utilization of the IHC algorithm (for normal traffic) at the expense of an increase in the time required for ATA reliable broadcast. We compare the IHC algorithm to several other possible virtual cut-through solutions and a store-and-forward solution. The IHC algorithm with the minimum value of /spl eta/ is shown to be optimal in minimizing the execution time of ATA reliable broadcast when used in a dedicated mode (with no other network traffic). >

62 citations


Cited by
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01 Apr 1997
TL;DR: The objective of this paper is to give a comprehensive introduction to applied cryptography with an engineer or computer scientist in mind on the knowledge needed to create practical systems which supports integrity, confidentiality, or authenticity.
Abstract: The objective of this paper is to give a comprehensive introduction to applied cryptography with an engineer or computer scientist in mind. The emphasis is on the knowledge needed to create practical systems which supports integrity, confidentiality, or authenticity. Topics covered includes an introduction to the concepts in cryptography, attacks against cryptographic systems, key use and handling, random bit generation, encryption modes, and message authentication codes. Recommendations on algorithms and further reading is given in the end of the paper. This paper should make the reader able to build, understand and evaluate system descriptions and designs based on the cryptographic components described in the paper.

2,188 citations

Journal ArticleDOI
TL;DR: This survey covers rollback-recovery techniques that do not require special language constructs and distinguishes between checkpoint-based and log-based protocols, which rely solely on checkpointing for system state restoration.
Abstract: This survey covers rollback-recovery techniques that do not require special language constructs. In the first part of the survey we classify rollback-recovery protocols into checkpoint-based and log-based.Checkpoint-based protocols rely solely on checkpointing for system state restoration. Checkpointing can be coordinated, uncoordinated, or communication-induced. Log-based protocols combine checkpointing with logging of nondeterministic events, encoded in tuples called determinants. Depending on how determinants are logged, log-based protocols can be pessimistic, optimistic, or causal. Throughout the survey, we highlight the research issues that are at the core of rollback-recovery and present the solutions that currently address them. We also compare the performance of different rollback-recovery protocols with respect to a series of desirable properties and discuss the issues that arise in the practical implementations of these protocols.

1,772 citations

Journal ArticleDOI
TL;DR: An in-depth study of the existing literature on data center power modeling, covering more than 200 models, organized in a hierarchical structure with two main branches focusing on hardware-centric and software-centric power models.
Abstract: Data centers are critical, energy-hungry infrastructures that run large-scale Internet-based services. Energy consumption models are pivotal in designing and optimizing energy-efficient operations to curb excessive energy consumption in data centers. In this paper, we survey the state-of-the-art techniques used for energy consumption modeling and prediction for data centers and their components. We conduct an in-depth study of the existing literature on data center power modeling, covering more than 200 models. We organize these models in a hierarchical structure with two main branches focusing on hardware-centric and software-centric power models. Under hardware-centric approaches we start from the digital circuit level and move on to describe higher-level energy consumption models at the hardware component level, server level, data center level, and finally systems of systems level. Under the software-centric approaches we investigate power models developed for operating systems, virtual machines and software applications. This systematic approach allows us to identify multiple issues prevalent in power modeling of different levels of data center systems, including: i) few modeling efforts targeted at power consumption of the entire data center ii) many state-of-the-art power models are based on a few CPU or server metrics, and iii) the effectiveness and accuracy of these power models remain open questions. Based on these observations, we conclude the survey by describing key challenges for future research on constructing effective and accurate data center power models.

741 citations