• Journal of the Korea Society of Computer and Information
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• v.16 no.9
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• pp.1-10
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• 2011

Unfortunately, in current microprocessors, increasing the frequency causes increased power consumption and reduced reliability whereas it improves the performance. To overcome the power and thermal problems in the singlecore processors, multicore processors has been widely used. For 2D multicore processors, interconnection is regarded as one of the major constraints in performance and power efficiency. To reduce the performance degradation and the power consumption in 2D multicore processors, 3D integrated design technique has been studied by many researchers. Compared to 2D multicore processors, 3D multicore processors get the benefits of performance improvement and reduced power consumption by reducing the wire length significantly. However, 3D multicore processors have serious thermal problems due to high power density, resulting in reliability degradation. Detailed thermal analysis for multicore processors can be useful in designing thermal-aware processors. In this paper, we analyze the impact of workload distribution, distance to the heat sink, and number of stacked dies on the processor temperature. We also analyze the effects of the temperature on overall system performance. Especially, this paper presents the guideline for thermal-aware multicore processor design by analyzing the thermal problems in 2D multicore processors and 3D multicore processors.

• Journal of the Korea Society of Computer and Information
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• v.15 no.11
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• pp.1-9
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• 2010

As the process technology scales down, an interconnection has became a major performance constraint for multi-core processors. Recently, in order to mitigate the performance bottleneck of the interconnection for multi-core processors, a 3D integration technique has drawn quite attention. The 3D integrated multi-core processor has advantage for reducing global wire length, resulting in a performance improvement. However, it causes serious thermal problems due to increased power density. For this reason, to design efficient 3D multi-core processors, thermal-aware design techniques should be considered. In this paper, we analyze the temperature on the 3D multi-core processors in function unit level through various experiments. We also present temperature characteristics by varying application features, cooling characteristics, and frequency levels on 3D multi-core processors. According to our experimental results, following two rules should be obeyed for thermal-aware 3D processor design. First, to optimize the thermal profile of cores, the core with higher cooling efficiency should be clocked at a higher frequency. Second, to lower the temperature of cores, a workload with higher thermal impact should be assigned to the core with higher cooling efficiency.

• The KIPS Transactions:PartA
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• v.17A no.6
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• pp.265-274
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• 2010

As the process technology scales down and integration densities continue to increase, interconnection has become one of the most important factors in performance of recent multi-core processors. Recently, to reduce the delay due to interconnection, 3D architecture has been adopted in designing multi-core processors. In 3D multi-core processors, multiple cores are stacked vertically and each core on different layers are connected by direct vertical TSVs(through-silicon vias). Compared to 2D multi-core architecture, 3D multi-core architecture reduces wire length significantly, leading to decreased interconnection delay and lower power consumption. Despite the benefits mentioned above, 3D design technique cannot be practical without proper solutions for hotspots due to high temperature. In this paper, we propose three floorplan schemes for reducing the peak temperature in 3D multi-core processors. According to our simulation results, the proposed floorplan schemes are expected to mitigate the thermal problems of 3D multi-core processors efficiently, resulting in improved reliability. Moreover, processor performance improves by reducing the performance degradation due to DTM techniques. Power consumption also can be reduced by decreased temperature and reduced execution time.

• Journal of the Korea Society of Computer and Information
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• v.16 no.6
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• pp.1-10
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• 2011

In designing multi-core processors, interconnection delay is one of the major constraints in performance improvement. To solve this problem, the 3-dimensional integration technology has been adopted in designing multi-core processors. The 3D multi-core architecture can reduce the physical wire length by stacking cores vertically, leading to reduced interconnection delay and reduced power consumption. However, the power density of 3D multi-core architecture is increased significantly compared to the traditional 2D multi-core architecture, resulting in the increased temperature of the processor. In this paper, the floorplan methods which change the forms of vertical placement of the core and the level-2 cache are analyzed to solve the thermal problems in 3D multi-core processors. According to the experimental results, it is an effective way to reduce the temperature in the processor that the core and the level-2 cache are stacked adjacently. Compared to the floorplan where cores are stacked adjacently to each other, the floorplan where the core is stacked adjacently to the level-2 cache can reduce the temperature by 22% in the case of 4-layers, and by 13% in the case of 2-layers.

• Journal of the Korea Society of Computer and Information
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• v.17 no.6
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• pp.1-11
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• 2012

As the process technology scales down, multi-core processors cause serious problems such as increased interconnection delay, high power consumption and thermal problems. To solve the problems in 2D multi-core processors, researchers have focused on the 3D multi-core processor architecture. Compared to the 2D multi-core processor, the 3D multi-core processor decreases interconnection delay by reducing wire length significantly, since each core on different layers is connected using vertical through-silicon via(TSV). However, the power density in the 3D multi-core processor is increased dramatically compared to that in the 2D multi-core processor, because multiple cores are stacked vertically. Unfortunately, increased power density causes thermal problems, resulting in high cooling cost, negative impact on the reliability. Therefore, temperature should be considered together with performance in designing 3D multi-core processors. In this work, we analyze the temperature of the cache in quad-core processors varying cache organization. Then, we propose the low-temperature cache organization to overcome the thermal problems. Our evaluation shows that peak temperature of the instruction cache is lower than threshold. The peak temperature of the data cache is higher than threshold when the cache is composed of many ways. According to the results, our proposed cache organization not only efficiently reduces the peak temperature but also reduces the performance degradation for 3D quad-core processors.

• Proceedings of the Korean Information Science Society Conference
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• 2011.06b
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• pp.5-8
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• 2011

3차원 멀티코어 프로세서는 기존의 멀티코어 프로세서에서 문제가 되던 연결망 지연시간과 전력문제를 해결할 수 있는 새로운 프로세서 설계기술이다. 하지만, 전력밀도의 증가로 인해 발생하는 열섬현상은 3차원 멀티코어 프로세서의 새로운 문제점으로 두드러지고 있다. 이러한 문제를 해결하기 위해서 동적 온도 관리 기법이 사용되지만, 동적 온도 관리 기법을 적용하면 시스템에 성능 저하가 발생하게 된다. 따라서 본 논문에서는 3차원 멀티코어 프로세서에서 문제가 되는 열섬현상을 해결하기 위해 고온의 유닛을 대상으로 동적 온도 관리 기법을 적용하고자 한다. 실험대상으로는 시스템 성능에 많은 영향을 미치고 높은 접근 때문에 고온이 발생하는 TLB 유닛을 사용하고자 한다. 특히, 시스템의 성능 저하를 줄이기 위해서 기존의 시스템보다 낮은 성능을 보이는 마이크로 TLB 구조를 적용해 보고자 한다. 성능이 낮은 구조의 경우 일반적으로 더 낮은 온도 분포를 보이며 동적 온도 관리 기법에 영향을 덜 받기 때문에 동적 온도 관리 기법만 적용한 구조보다 더 낮은 성능 저하를 보일 수 있다. 실험결과 동적 온도 관리 기법을 적용한 경우 기존의 시스템에 비해 23.4%의 성능 저하가 발생하고 마이크로 TLB 구조를 적용한 경우 27.1%의 성능 저하가 발생함을 알 수 있다.

• The Journal of the Institute of Internet, Broadcasting and Communication
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• v.13 no.4
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• pp.171-177
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• 2013

Due to the demand for high speed 3D graphic rendering, video file format conversion, compression, encryption and decryption technologies, the importance of digital signal processor system is growing rapidly. In order to satisfy the real-time constraints, high performance digital signal processor is required. Therefore, as in general purpose computer systems, digital signal processor should be designed as multicore architecture as well. Using UTDSP benchmarks as input, the trace-driven simulation has been performed and analyzed for the 2 to 16-core digital signal processor architectures with the cores from simple RISC to in-order and out-of-order superscalar processors for the various window sizes, extensively.

• The KIPS Transactions:PartA
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• v.19A no.2
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• pp.77-84
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• 2012

Speculative execution for improving instruction-level parallelism is widely used in high-performance processors. In the speculative execution technique, the most important factor is the accuracy of branch predictor. Unfortunately, complex branch predictors for improving the accuracy can cause serious thermal problems in 3D multicore processors. Thermal problems have negative impact on the processor performance. This paper analyzes two methods to solve the thermal problems in the branch predictor of 3D multi-core processors. First method is dynamic thermal management which turns off the execution of the branch predictor when the temperature of the branch predictor exceeds the threshold. Second method is thermal-aware branch predictor placement policy by considering each layer's temperature in 3D multi-core processors. According to our evaluation, the branch predictor placement policy shows that average temperature is $87.69^{\circ}C$, and average maximum temperature gradient is $11.17^{\circ}C$. And, dynamic thermal management shows that average temperature is $89.64^{\circ}C$ and average maximum temperature gradient is $17.62^{\circ}C$. Proposed branch predictor placement policy has superior thermal efficiency than the dynamic thermal management. In the perspective of performance, the proposed branch predictor placement policy degrades the performance by 3.61%, while the dynamic thermal management degrades the performance by 27.66%.