상변화 메모리 시스템의 간섭 오류 완화 및 RMW 성능 향상 기법

학위논문(박사) -- 서울대학교대학원 : 공과대학 전기·정보공학부, 2021.8. 이혁재.Phase-change memory (PCM) announces the beginning of the new era of memory systems, owing to attractive characteristics. Many memory product manufacturers (e.g., Intel, SK Hynix, and Samsung) are developing related products. PCM can be applied to various circumstances; it is not simply limited to an extra-scale database. For example, PCM has a low standby power due to its non-volatility; hence, computation-intensive applications or mobile applications (i.e., long memory idle time) are suitable to run on PCM-based computing systems. Despite these fascinating features of PCM, PCM is still far from the general commercial market due to low reliability and long latency problems. In particular, low reliability is a painful problem for PCM in past decades. As the semiconductor process technology rapidly scales down over the years, DRAM reaches 10 nm class process technology. In addition, it is reported that the write disturbance error (WDE) would be a serious issue for PCM if it scales down below 54 nm class process technology. Therefore, addressing the problem of WDEs becomes essential to make PCM competitive to DRAM. To overcome this problem, this dissertation proposes a novel approach that can restore meta-stable cells on demand by levering two-level SRAM-based tables, thereby significantly reducing the number WDEs. Furthermore, a novel randomized approach is proposed to implement a replacement policy that originally requires hundreds of read ports on SRAM. The second problem of PCM is a long-latency compared to that of DRAM. In particular, PCM tries to enhance its throughput by adopting a larger transaction unit; however, the different unit size from the general-purpose processor cache line further degrades the system performance due to the introduction of a read-modify-write (RMW) module. Since there has never been any research related to RMW in a PCM-based memory system, this dissertation proposes a novel architecture to enhance the overall system performance and reliability of a PCM-based memory system having an RMW module. The proposed architecture enhances data re-usability without introducing extra storage resources. Furthermore, a novel operation that merges commands regardless of command types is proposed to enhance performance notably. Another problem is the absence of a full simulation platform for PCM. While the announced features of the PCM-related product (i.e., Intel Optane) are scarce due to confidential issues, all priceless information can be integrated to develop an architecture simulator that resembles the available product. To this end, this dissertation tries to scrape up all available features of modules in a PCM controller and implement a dedicated simulator for future research purposes.상변화 메모리는(PCM) 매력적인 특성을 통해 메모리 시스템의 새로운 시대의 시작을 알렸다. 많은 메모리 관련 제품 제조업체(예 : 인텔, SK 하이닉스, 삼성)가 관련 제품 개발에 박차를 가하고 있다. PCM은 단순히 대규모 데이터베이스에만 국한되지 않고 다양한 상황에 적용될 수 있다. 예를 들어, PCM은 비휘발성으로 인해 대기 전력이 낮다. 따라서 계산 집약적인 애플리케이션 또는 모바일 애플리케이션은(즉, 긴 메모리 유휴 시간) PCM 기반 컴퓨팅 시스템에서 실행하기에 적합하다. PCM의 이러한 매력적인 특성에도 불구하고 PCM은 낮은 신뢰성과 긴 대기 시간으로 인해 여전히 일반 산업 시장에서는 DRAM과 다소 격차가 있다. 특히 낮은 신뢰성은 지난 수십 년 동안 PCM 기술의 발전을 저해하는 문제다. 반도체 공정 기술이 수년에 걸쳐 빠르게 축소됨에 따라 DRAM은 10nm 급 공정 기술에 도달하였다. 이어서, 쓰기 방해 오류 (WDE)가 54nm 등급 프로세스 기술 아래로 축소되면 PCM에 심각한 문제가 될 것으로 보고되었다. 따라서, WDE 문제를 해결하는 것은 PCM이 DRAM과 동등한 경쟁력을 갖추도록 하는 데 있어 필수적이다. 이 문제를 극복하기 위해 이 논문에서는 2-레벨 SRAM 기반 테이블을 활용하여 WDE 수를 크게 줄여 필요에 따라 준 안정 셀을 복원할 수 있는 새로운 접근 방식을 제안한다. 또한, 원래 SRAM에서 수백 개의 읽기 포트가 필요한 대체 정책을 구현하기 위해 새로운 랜덤 기반의 기법을 제안한다. PCM의 두 번째 문제는 DRAM에 비해 지연 시간이 길다는 것이다. 특히 PCM은 더 큰 트랜잭션 단위를 채택하여 단위시간 당 데이터 처리량 향상을 도모한다. 그러나 범용 프로세서 캐시 라인과 다른 유닛 크기는 읽기-수정-쓰기 (RMW) 모듈의 도입으로 인해 시스템 성능을 저하하게 된다. PCM 기반 메모리 시스템에서 RMW 관련 연구가 없었기 때문에 본 논문은 RMW 모듈을 탑재 한 PCM 기반 메모리 시스템의 전반적인 시스템 성능과 신뢰성을 향상하게 시킬 수 있는 새로운 아키텍처를 제안한다. 제안된 아키텍처는 추가 스토리지 리소스를 도입하지 않고도 데이터 재사용성을 향상시킨다. 또한, 성능 향상을 위해 명령 유형과 관계없이 명령을 병합하는 새로운 작업을 제안한다. 또 다른 문제는 PCM을 위한 완전한 시뮬레이션 플랫폼이 부재하다는 것이다. PCM 관련 제품(예 : Intel Optane)에 대해 발표된 정보는 대외비 문제로 인해 부족하다. 하지만 알려져 있는 정보를 적절히 취합하면 시중 제품과 유사한 아키텍처 시뮬레이터를 개발할 수 있다. 이를 위해 본 논문은 PCM 메모리 컨트롤러에 필요한 모든 모듈 정보를 활용하여 향후 이와 관련된 연구에서 충분히 사용 가능한 전용 시뮬레이터를 구현하였다.1 INTRODUCTION 1 1.1 Limitation of Traditional Main Memory Systems 1 1.2 Phase-Change Memory as Main Memory 3 1.2.1 Opportunities of PCM-based System 3 1.2.2 Challenges of PCM-based System 4 1.3 Dissertation Overview 7 2 BACKGROUND AND PREVIOUS WORK 8 2.1 Phase-Change Memory 8 2.2 Mitigation Schemes for Write Disturbance Errors 10 2.2.1 Write Disturbance Errors 10 2.2.2 Verification and Correction 12 2.2.3 Lazy Correction 13 2.2.4 Data Encoding-based Schemes 14 2.2.5 Sparse-Insertion Write Cache 16 2.3 Performance Enhancement for Read-Modify-Write 17 2.3.1 Traditional Read-Modify-Write 17 2.3.2 Write Coalescing for RMW 19 2.4 Architecture Simulators for PCM 21 2.4.1 NVMain 21 2.4.2 Ramulator 22 2.4.3 DRAMsim3 22 3 IN-MODULE DISTURBANCE BARRIER 24 3.1 Motivation 25 3.2 IMDB: In Module-Disturbance Barrier 29 3.2.1 Architectural Overview 29 3.2.2 Implementation of Data Structures 30 3.2.3 Modification of Media Controller 36 3.3 Replacement Policy 38 3.3.1 Replacement Policy for IMDB 38 3.3.2 Approximate Lowest Number Estimator 40 3.4 Putting All Together: Case Studies 43 3.5 Evaluation 45 3.5.1 Configuration 45 3.5.2 Architectural Exploration 47 3.5.3 Effectiveness of the Replacement Policy 48 3.5.4 Sensitivity to Main Table Configuration 49 3.5.5 Sensitivity to Barrier Buffer Size 51 3.5.6 Sensitivity to AppLE Group Size 52 3.5.7 Comparison with Other Studies 54 3.6 Discussion 59 3.7 Summary 63 4 INTEGRATION OF AN RMW MODULE IN A PCM-BASED SYSTEM 64 4.1 Motivation 65 4.2 Utilization of DRAM Cache for RMW 67 4.2.1 Architectural Design 67 4.2.2 Algorithm 70 4.3 Typeless Command Merging 73 4.3.1 Architectural Design 73 4.3.2 Algorithm 74 4.4 An Alternative Implementation: SRC-RMW 78 4.4.1 Implementation of SRC-RMW 78 4.4.2 Design Constraint 80 4.5 Case Study 82 4.6 Evaluation 85 4.6.1 Configuration 85 4.6.2 Speedup 88 4.6.3 Read Reliability 91 4.6.4 Energy Consumption: Selecting a Proper Page Size 93 4.6.5 Comparison with Other Studies 95 4.7 Discussion 97 4.8 Summary 99 5 AN ALL-INCLUSIVE SIMULATOR FOR A PCM CONTROLLER 100 5.1 Motivation 101 5.2 PCMCsim: PCM Controller Simulator 103 5.2.1 Architectural Overview 103 5.2.2 Underlying Classes of PCMCsim 104 5.2.3 Implementation of Contention Behavior 108 5.2.4 Modules of PCMCsim 109 5.3 Evaluation 116 5.3.1 Correctness of the Simulator 116 5.3.2 Comparison with Other Simulators 117 5.4 Summary 119 6 Conclusion 120 Abstract (In Korean) 141 Acknowledgment 143박

상변화 메모리 시스템의 간섭 오류 완화 및 RMW 성능 향상 기법

학위논문(박사)--서울대학교 대학원 :공과대학 전기·정보공학부,2021. 8. 이혁재.Phase-change memory (PCM) announces the beginning of the new era of memory systems, owing to attractive characteristics. Many memory product manufacturers (e.g., Intel, SK Hynix, and Samsung) are developing related products. PCM can be applied to various circumstances; it is not simply limited to an extra-scale database. For example, PCM has a low standby power due to its non-volatility; hence, computation-intensive applications or mobile applications (i.e., long memory idle time) are suitable to run on PCM-based computing systems. The second problem of PCM is a long-latency compared to that of DRAM. In particular, PCM tries to enhance its throughput by adopting a larger transaction unit; however, the different unit size from the general-purpose processor cache line further degrades the system performance due to the introduction of a read-modify-write (RMW) module. Since there has never been any research related to RMW in a PCM-based memory system, this dissertation proposes a novel architecture to enhance the overall system performance and reliability of a PCM-based memory system having an RMW module. The proposed architecture enhances data re-usability without introducing extra storage resources. Furthermore, a novel operation that merges commands regardless of command types is proposed to enhance performance notably.Despite these fascinating features of PCM, PCM is still far from the general commercial market due to low reliability and long latency problems. In particular, low reliability is a painful problem for PCM in past decades. As the semiconductor process technology rapidly scales down over the years, DRAM reaches 10 nm class process technology. In addition, it is reported that the write disturbance error (WDE) would be a serious issue for PCM if it scales down below 54 nm class process technology. Therefore, addressing the problem of WDEs becomes essential to make PCM competitive to DRAM. To overcome this problem, this dissertation proposes a novel approach that can restore meta-stable cells on demand by levering two-level SRAM-based tables, thereby significantly reducing the number WDEs. Furthermore, a novel randomized approach is proposed to implement a replacement policy that originally requires hundreds of read ports on SRAM.Another problem is the absence of a full simulation platform for PCM. While the announced features of the PCM-related product (i.e., Intel Optane) are scarce due to confidential issues, all priceless information can be integrated to develop an architecture simulator that resembles the available product. To this end, this dissertation tries to scrape up all available features of modules in a PCM controller and implement a dedicated simulator for future research purposes

(A) clinical evaluation of splanchnic nerve block with absolute ethanol

의학과/박사[한글] 상복부 암성통증에 대해 알코올에 의한 내장신경차단이 유효함은 널리 알려진 사실이다. 그러나 국소마취제에 의한 시험차단후 주입 알코올 농도에 따른 효과에 대해서는 아직도 확실치 않다. 본 연구는 상복부 암성통증 제거를 목적으로 1997년 9월부터 1991년 4월까지 1% lidocaine 주입으로 차단효과 확인후 약 20분후에 무수 알코올을 주입하여 내장신경차단을 시행받은 33예를 대상으로 하였다. 환자의 성별 및 연령별 분포, 질환별 분포, 통증부위, 차단전 항암치료상황, 차단 전 및 후의 진통제 투약상황, 1회 및 반복차단시 제통효과, 차단간 기간, 합병증, 내장신경차단 전 및 후에 시행한 병용치료요법의 종류 및 차단후 퇴원까지의 기간 등을 조사 분석하여 다음의 결과를 얻었다. 1)무수 알코올에 의한 내장신경차단을 받은 환자의 남녀비는 2 : 1 이었으며, 연령별로는 50대가 45.5%로 가장 많았다. 2) 무수 알코올에 의한 내장신경 차단을 시행받은 환자의 질환별 분포는 위암(39.4%), 췌장암(27.3%) 및 간암(15.2%)의 순이었다. 3) 무수 알코올에 의한 내장신경차단전 대상환자의 통증부위는 상복부(67.O%). 명치부(24.7%) 및 복부전체(9.1%)의 순이었다. 4) 무수알코올에 의한 내장신경차단전 항암치료 상황은 외과적 수술과 화타요법을 병행한 예 및 화타요법을 단독으로 시행한 예가 각각 24.2%로 가장 많았고, 외과적 수술만 시행한 예가 9.1%, 방사선치료만 시행한 예 및 화학요법과 방사선치료를 시행한 예가 각각 3.O%였다. 5) 무수 알코올에 의한 내장신경차단을 시행받은 환자의 1회차단후 제통효과는 84.8%로 비교적 양호하였으며, 2주 이내에 통증이 재발한 예에서 시행한 2회 및 3회 반복차단시 제통효과는 각각 80.7%및 lOO%였다. 6) 1회 차단전 아편계 진통제를 투약받은 예는 11예(33.3%)였으며, 이중 3예(6.1%)에서 차단후 아편계 진통제를 투약 받았다. 2회 반복차단한 7예중 차단전 4예(57.1%) 그리고 차단후 3예(42.9%)에서 아편계 진통제를 투여 받았다. 7) 2회 반복차단시 차단간 간격은 2주 이내가 5예(71.4%)로 가장 많았으며, 3개월 및 6개월이 각각 1예(14.3%) 있었다. 8) 무수 알코올에 의한 내장신경차단시 발현된 합병증은 저혈압이 11예(33.3%), 알코올 주입시의 통증이 5예(15.2%), 안면홍조 및 주사부위통증이 각각 3예(9.1%), 구역과 구토 및 호흡곤란이 각각 2예(6.1%) 그리고 흉부불편감 및 설사가 각각 1예(3.O%)가 있었다. 9) 무수 알코올에 의한 내장신경차단전 시행한 보조 치료요법으로는 지속적경막외차단이 90.9%로서 가장 많았다. 이상의 결과를 종합하여 볼때, 1% lidocaine에 의한 시험차단 약 20분후 무수 알코올을 양측에 각각 12m1씩 주입하여 시행한 내장신경차단시 1회차단후 재통효과는 84.8%로서 만족스런 결과였으나, 재차단율이 15.2%였다. 그 이유에 대해서는 확실치 않으나 아마도 적은 용량의 알코올로 인해 알코올의 퍼짐이 불충분하여 내장신경을 충분히 차단하지 못했던 것으로 추측된다. 따라서 앞으로 더 많은 예에서 알코올의 주입용량을 늘려서 그 제 통효과를 추구해야 될것으로 사료된다. [영문] It has been well known that the splanchnic nerve block is effective for patients who suffer from intractable upper abdominal pain. However, It is unclear whether the effect of the splanchnic nerve block depends on varied alcoholic concentration. In thin study, an attempt was made to use absolute ethanol on patients who recieved a splanchnic nerve block at Severance Hospital during the period from September 1990 to April 1991. The results are as for follows: 1) Among the 33 patients, including 22 males and 11 females, the fifties and sixties were the major age groups. 2) Stomach cancer was the most common underlying disease(13 cased), with pancreatic cancer next(9 cases). 3) The main locations of pain were the upper abdomen, epigastrium, and etire abdomen in decreasing order. 4) There were 17 cases who had had chemotherapy, and 11 cases of whom had had surgery before the splanchnic nerve block. 5) The volume of alcohol used was 12m1 hi laterally. 6) Among the 33 patients, 15.2% required a second block within two weeks of the first block. One case required a third block. 7) The most common complications of splanchnic nerve block were hypotension(33.3%), occasional transient sharp burning pain, flushing of face, pain on injection site, nausea, vomiting, dyepnea, chest discomfort and diarrhea. 8) The supplemental block most commonly used was a continuous epidural block. It was used both as a diagnostic block and to afford relief from pain before the splanchnic nerve block was drone. 9) The interval between the receiving the absolute ethanol block and discharge was within 2 weeks in 15 cases. But, in the patients with poor genera1 heal th, the interval between the splanchnic nerve block and discharge was prolonged. The above results suggest that bilateral splanchnic nerve block done with absolute ethanol block after an effective test block with 1% lidocaine under C-arm fluroscopic control is satisfactory and reliable. Still, 26.6% of the patients received a repeat block within 2 weeks. Insufficient spread of alcohol due to its small volume seems to be a major factor In the repeat block. Minimizing the incidence of repeat block remains a problem to be solyed.restrictio

고강도강의 수소 유기 파괴 과정에 관한 연구

학위논문(박사) - 한국과학기술원 : 재료공학과, 1990.2, [ vi, 128 p. ]The equilibrium and propagation kinetics, which are characterized in terms of the threshold stress intensity and crack propagation rate, respectively, of hydrogen-assisted cracking in high-strength steels have been investigated in gaseous and aqueous environments. The threshold stress intensity and the crack propagation rate depended strongly on the hydrogen pressure, temperature, yield strength and impurity level, From both the fractographic analysis and micromechanistic consideration for the respective fracture modes, in particular, the concepts underlying fracture mode transition for hydrogen-assisted cracking in high-strength steel have been proposed. In chapter Ⅲ, fracture mode transition in hydrogen-assisted cracking (HAC) of AISI 4340 steel has been studied from equilibrium aspects at room temperature with 8.6 mm thick double cantilever beam(DCB) specimens. The threshold stress intensity $K_{th}$ necessary for the occurrence of HAC and the corresponding fracture surface morphology have been determined as a function of hydrogen pressure and yield strength. The $K_{th}$ necessary for the occurrence of HAC increased with decrease in hydrogen pressure at a given yield strength and also with decrease in yield strength at a given hydrogen pressure. As $K_{th}$ increased, the corresponding HAC fracture mode changed from intergranular (IG) and quasi-cleavage (QC) modes to the microvoid coalescence (MVC) mode. The experimental results indicate that the critical hydrogen concentration for crack extension accompanied by the IG mode is higher than that for crack extension accompanied by the MVC mode. the fracture mode transition with varying hydrogen pressure and yield strength is discussed simultaneously in terms of the micromechanisms for HAC and the hydrogen pressure and yield strength dependencies of the $k_{th}$ From the present experimental results, it seems that the HAC fracture mode of high-strength steels is primarily determined by the applied stress inten...한국과학기술원 : 재료공학과

유동효과를 고려한 얇은 평판에서의 음향방사 및 모드연성효과에 관한 연구

학위논문(박사) - 한국과학기술원 : 기계공학과, 1994.8, [ xxi, 149 p. ]Naval and aerodynamic designers are concerned about the sound radiated from vibrating complex structures in heavy or light fluid medium excited by broadband random forces, that is, mechanical forces or turbulent boundary layer (TBL) pressure fluctuations. They wish to minimize significant noise radiation both outward to the medium and inward to the structure inside. Hence a method for computing the vibroacoustic response of structures acted by broadband random forces is of critical value to the designer by permitting him to select appropriate structural modifications (e.g. damping treatments) or to apply appropriate mechanical forces to structures to suppress structural vibration and the associated radiation of sound. Accurate methods of computation for the vibroacoustic response of the key components of complex structures such as plates and cylinders excited by random forces will provide a useful foundation extensible to more complex structures, e.g. airplane fuselage-wing systems, missiles, ribbed sonar domes, and ship-hull systems, etc. This thesis presents theoretical formulations of acoustic radiation from rectangular plates with a few ideal edge conditions in heavy and light fluid media excited by random forces, that is, arbitrary mechanical forces or turbulent boundary layer pressure fluctuations, in the presence of a uniform subsonic flow. This analysis is based on in vacuo modal expansion of both the plate vibration and the pressure fields. The plate vibration and the pressure fields described in modal domain are transformed into wavenumber-frequency domain. Numerical evaluation of the acoustic power is extremely time-consuming for broadband excitations. In order to obtain the approximate solutions, it is assumed that the broadband forcing functions have white spectra and remain unaltered due to the plate vibration and that the modal coupling is weak as long as structural damping is light. Under these assumptions, the approximate solutions for the surf...한국과학기술원 : 기계공학과

비점성 유체와 접촉하는 고정 층원판으로부터의 음향방사 해석에 관한 연구

학위논문(석사) - 한국과학기술원 : 기계공학과, 1988.2, [ vi, 47 p. ]It is well known that the vibration induced acoustic pressure in an acoustic fluid can be theoretically calculated by Rayleigh integral techniques. But it needs a lot of calculations since it contains integral form equations. In this study, an alternative calculation method was suggested by using Timoshenko-Mindlin plate theory. The governing equations for circular plate vibration and acoustic pressure were simultaneously constructed. The solutions to the coupled equations can be obtained by the proper coordinate transformations. In order to show the effectiveness of the method, this technique was applied to a clamped layered circular plate with structural damping in contact with an inviscid fluid, and so the nearfield and the farfield pressure in the fluid and radiated power were calculated.한국과학기술원 : 기계공학과