Fast, Accurate and Detailed NoC Simulations

Network-on-Chip (NoC) architectures have a wide variety of parameters that can be adapted to the designer's requirements. Fast exploration of this parameter space is only possible at a high-level and several methods have been proposed. Cycle and bit accurate simulation is necessary when the actual router's RTL description needs to be evaluated and verified. However, extensive simulation of the NoC architecture with cycle and bit accuracy is prohibitively time consuming. In this paper we describe a simulation method to simulate large parallel homogeneous and heterogeneous network-on-chips on a single FPGA. The method is especially suitable for parallel systems where lengthy cycle and bit accurate simulations are required. As a case study, we use a NoC that was modelled and simulated in SystemC. We simulate the same NoC on the described FPGA simulator. This enables us to observe the NoC behavior under a large variety of traffic patterns. Compared with the SystemC simulation we achieved a speed-up of 80-300, without compromising the cycle and bit level accuracy

Network-on-Chip -based Multi-Processor System-on-Chip: Towards Mixed-Criticality System Certification

L'abstract è presente nell'allegato / the abstract is in the attachmen

Heracles: Fully Synthesizable Parameterized MIPS-Based Multicore System

Heracles is an open-source complete multicore system written in Verilog. It is fully parameterized and can be reconfigured and synthesized into different topologies and sizes. Each processing node has a 7-stage pipeline, fully bypassed, microprocessor running the MIPS-III ISA, a 4-stage input-buffer, virtual-channel router, and a local variable-size shared memory. Our design is highly modular with clear interfaces between the core, the memory hierarchy, and the on-chip network. In the baseline design, the microprocessor is attached to two caches, one instruction cache and one data cache, which are oblivious to the global memory organization. The memory system in Heracles can be configured as one single global shared memory (SM), or distributed shared memory (DSM), or any combination thereof. Each core is connected to the rest of the network of processors by a parameterized, realistic, wormhole router. We show different topology configurations of the system, and their synthesis results on the Xilinx Virtex-5 LX330T FPGA board. We also provide a small MIPS cross-compiler toolchain to assist in developing software for Heracles

An Energy-Efficient Reconfigurable Circuit Switched Network-on-Chip

Network-on-Chip (NoC) is an energy-efficient on-chip communication architecture for multi-tile System-on-Chip (SoC) architectures. The SoC architecture, including its run-time software, can replace inflexible ASICs for future ambient systems. These ambient systems have to be flexible as well as energy-efficient. To find an energy-efficient solution for the communication network we analyze three wireless applications. Based on their communication requirements we observe that revisiting of the circuit switching techniques is beneficial. In this paper we propose a new energy-efficient reconfigurable circuit-switched Network-on-Chip. By physically separating the concurrent data streams we reduce the overall energy consumption. The circuit-switched router has been synthesized and analyzed for its power consumption in 0.13 ¿m technology. A 5-port circuit-switched router has an area of 0.05 mm2 and runs at 1075 MHz. The proposed architecture consumes 3.5 times less energy compared to its packet-switched equivalen

Heracles: A Tool for Fast RTL-Based Design Space Exploration of Multicore Processors

This paper presents Heracles, an open-source, functional, parameterized, synthesizable multicore system toolkit. Such a multi/many-core design platform is a powerful and versatile research and teaching tool for architectural exploration and hardware-software co-design. The Heracles toolkit comprises the soft hardware (HDL) modules, application compiler, and graphical user interface. It is designed with a high degree of modularity to support fast exploration of future multicore processors of di erent topologies, routing schemes, processing elements (cores), and memory system organizations. It is a component-based framework with parameterized interfaces and strong emphasis on module reusability. The compiler toolchain is used to map C or C++ based applications onto the processing units. The GUI allows the user to quickly con gure and launch a system instance for easy factorial development and evaluation. Hardware modules are implemented in synthesizable Verilog and are FPGA platform independent. The Heracles tool is freely available under the open-source MIT license at: http://projects.csail.mit.edu/heracle

On Energy Efficient Computing Platforms

In accordance with the Moore's law, the increasing number of on-chip integrated transistors has enabled modern computing platforms with not only higher processing power but also more affordable prices. As a result, these platforms, including portable devices, work stations and data centres, are becoming an inevitable part of the human society. However, with the demand for portability and raising cost of power, energy efficiency has emerged to be a major concern for modern computing platforms. As the complexity of on-chip systems increases, Network-on-Chip (NoC) has been proved as an efficient communication architecture which can further improve system performances and scalability while reducing the design cost. Therefore, in this thesis, we study and propose energy optimization approaches based on NoC architecture, with special focuses on the following aspects. As the architectural trend of future computing platforms, 3D systems have many bene ts including higher integration density, smaller footprint, heterogeneous integration, etc. Moreover, 3D technology can signi cantly improve the network communication and effectively avoid long wirings, and therefore, provide higher system performance and energy efficiency. With the dynamic nature of on-chip communication in large scale NoC based systems, run-time system optimization is of crucial importance in order to achieve higher system reliability and essentially energy efficiency. In this thesis, we propose an agent based system design approach where agents are on-chip components which monitor and control system parameters such as supply voltage, operating frequency, etc. With this approach, we have analysed the implementation alternatives for dynamic voltage and frequency scaling and power gating techniques at different granularity, which reduce both dynamic and leakage energy consumption. Topologies, being one of the key factors for NoCs, are also explored for energy saving purpose. A Honeycomb NoC architecture is proposed in this thesis with turn-model based deadlock-free routing algorithms. Our analysis and simulation based evaluation show that Honeycomb NoCs outperform their Mesh based counterparts in terms of network cost, system performance as well as energy efficiency.Siirretty Doriast

Design Space Exploration of Accelerators for Warehouse Scale Computing

With Moore’s law grinding to a halt, accelerators are one of the ways that new silicon can improve performance, and they are already a key component in modern datacenters. Accelerators are integrated circuits that implement parts of an application with the objective of higher energy efficiency compared to execution on a standard general purpose CPU. Many accelerators can target any particular workload, generally with a wide range of performance, and costs such as area or power. Exploring these design choices, called Design Space Exploration (DSE), is a crucial step in trying to find the most efficient accelerator design, the one that produces the largest reduction of the total cost of ownership. This work aims to improve this design space exploration phase for accelerators and to avoid pitfalls in the process. This dissertation supports the thesis that early design choices – including the level of specialization – are critical for accelerator development and therefore require benchmarks reflective of production workloads. We present three studies that support this thesis. First, we show how to benchmark datacenter applications by creating a benchmark for large video sharing infrastructures. Then, we present two studies focused on accelerators for analytical query processing. The first is an analysis on the impact of Network on Chip specialization while the second analyses the impact of the level of specialization. The first part of this dissertation introduces vbench: a video transcoding benchmark tailored to the growing video-as-a-service market. Video transcoding is not accurately represented in current computer architecture benchmarks such as SPEC or PARSEC. Despite posing a big computational burden for cloud video providers, such as YouTube and Facebook, it is not included in cloud benchmarks such as CloudSuite. Using vbench, we found that the microarchitectural profile of video transcoding is highly dependent on the input video, that SIMD extensions provide limited benefits, and that commercial hardware transcoders impose tradeoffs that are not ideal for cloud video providers. Our benchmark should spur architectural innovations for this critical workload. This work shows how to benchmark a real world warehouse scale application and the possible pitfalls in case of a mischaracterization. When considering accelerators for the different, but no less important, application of analytical query processing, design space exploration plays a critical role. We analyzed the Q100, a class of accelerators for this application domain, using TPC-H as the reference benchmark. We found that the hardware computational blocks have to be tailored to the requirements of the application, but also the Network on Chip (NoC) can be specialized. We developed an algorithm capable of producing more effective Q100 designs by tailoring the NoC to the communication requirements of the system. Our algorithm is capable of producing designs that are Pareto optimal compared to standard NoC topologies. This shows how NoC specialization is highly effective for accelerators and it should be an integral part of design space exploration for large accelerators’ designs. The third part of this dissertation analyzes the impact of the level of specialization, e.g. using an ASIC or Coarse Grain Reconfigurable Architecture (CGRA) implementation, on an accelerator performance. We developed a CGRA architecture capable of executing SQL query plans. We compare this architecture against Q100, an ASIC that targets the same class of workloads. Despite being less specialized, this programmable architecture shows comparable performance to the Q100 given an area and power budget. Resource usage explains this counterintuitive result, since a well programmed, homogeneous array of resources is able to more effectively harness silicon for the workload at hand. This suggests that a balanced accelerator research portfolio must include alternative programmable architectures – and their software stacks

Automatic synthesis and optimization of chip multiprocessors

The microprocessor technology has experienced an enormous growth during the last decades. Rapid downscale of the CMOS technology has led to higher operating frequencies and performance densities, facing the fundamental issue of power dissipation. Chip Multiprocessors (CMPs) have become the latest paradigm to improve the power-performance efficiency of computing systems by exploiting the parallelism inherent in applications. Industrial and prototype implementations have already demonstrated the benefits achieved by CMPs with hundreds of cores.CMP architects are challenged to take many complex design decisions. Only a few of them are:- What should be the ratio between the core and cache areas on a chip?- Which core architectures to select?- How many cache levels should the memory subsystem have?- Which interconnect topologies provide efficient on-chip communication?These and many other aspects create a complex multidimensional space for architectural exploration. Design Automation tools become essential to make the architectural exploration feasible under the hard time-to-market constraints. The exploration methods have to be efficient and scalable to handle future generation on-chip architectures with hundreds or thousands of cores.Furthermore, once a CMP has been fabricated, the need for efficient deployment of the many-core processor arises. Intelligent techniques for task mapping and scheduling onto CMPs are necessary to guarantee the full usage of the benefits brought by the many-core technology. These techniques have to consider the peculiarities of the modern architectures, such as availability of enhanced power saving techniques and presence of complex memory hierarchies.This thesis has several objectives. The first objective is to elaborate the methods for efficient analytical modeling and architectural design space exploration of CMPs. The efficiency is achieved by using analytical models instead of simulation, and replacing the exhaustive exploration with an intelligent search strategy. Additionally, these methods incorporate high-level models for physical planning. The related contributions are described in Chapters 3, 4 and 5 of the document.The second objective of this work is to propose a scalable task mapping algorithm onto general-purpose CMPs with power management techniques, for efficient deployment of many-core systems. This contribution is explained in Chapter 6 of this document.Finally, the third objective of this thesis is to address the issues of the on-chip interconnect design and exploration, by developing a model for simultaneous topology customization and deadlock-free routing in Networks-on-Chip. The developed methodology can be applied to various classes of the on-chip systems, ranging from general-purpose chip multiprocessors to application-specific solutions. Chapter 7 describes the proposed model.The presented methods have been thoroughly tested experimentally and the results are described in this dissertation. At the end of the document several possible directions for the future research are proposed

Architectural Support for Efficient Communication in Future Microprocessors

Traditionally, the microprocessor design has focused on the computational aspects of the problem at hand. However, as the number of components on a single chip continues to increase, the design of communication architecture has become a crucial and dominating factor in defining performance models of the overall system. On-chip networks, also known as Networks-on-Chip (NoC), emerged recently as a promising architecture to coordinate chip-wide communication. Although there are numerous interconnection network studies in an inter-chip environment, an intra-chip network design poses a number of substantial challenges to this well-established interconnection network field. This research investigates designs and applications of on-chip interconnection network in next-generation microprocessors for optimizing performance, power consumption, and area cost. First, we present domain-specific NoC designs targeted to large-scale and wire-delay dominated L2 cache systems. The domain-specifically designed interconnect shows 38% performance improvement and uses only 12% of the mesh-based interconnect. Then, we present a methodology of communication characterization in parallel programs and application of characterization results to long-channel reconfiguration. Reconfigured long channels suited to communication patterns enhance the latency of the mesh network by 16% and 14% in 16-core and 64-core systems, respectively. Finally, we discuss an adaptive data compression technique that builds a network-wide frequent value pattern map and reduces the packet size. In two examined multi-core systems, cache traffic has 69% compressibility and shows high value sharing among flows. Compression-enabled NoC improves the latency by up to 63% and saves energy consumption by up to 12%

LBDR: An efficient unicast routing support for CMPs

LBDR is a routing distributed layer based on minimum logic that removes the need for routing tables at switches on network-on-chips (NoCs) in CMPs and enables the implementation of many routing algorithms on most of regular and irregular toplogies we may find in the near future in a multi-core system.Rodrigo Mocholí, S. (2008). LBDR: An efficient unicast routing support for CMPs. http://hdl.handle.net/10251/13476Archivo delegad