3D ultrasound, an emerging medical imaging technique that is presently only used in hospitals, has the potential to enable breakthrough telemedicine applications, provided that its cost and power dissipation can be minimized. In this paper, we present an FPGA architecture suitable for a portable medical 3D ultrasound device. We show an optimized design for the digital part of the imager, including the delay calculation block, which is its most critical part. Our computationally efficient approach requires a single FPGA for 3D imaging, which is unprecedented. The design is scalable; a configuration supporting a 32×32-channel probe, which enables high-quality imaging, consumes only about 5W.

We present an efficient FPGA architecture suitable for a medical 3D ultrasound beamformer. We tackle the delay calculation bottleneck, which is the heart and the most critical part of the beamformer, by proposing a computationally efficient design that is able to perform volumetric real-time beamforming on a single-chip FPGA. The design has been demonstrated for a 32×32-channel receive probe, and we extrapolated the requirements of the architecture for 80×80 channels.

In medical diagnosis, ultrasound (US) imaging is one of the most common, safe, and powerful techniques. Volumetric (3D) US imaging, an emerging technique, is even more attractive than standard 2D imaging, as it allows for imaging without the local presence of a trained sonographer finely positioning the probe. This would be particularly useful in rescue operations, remote areas and developing countries. Unfortunately, present-day 3D imagers are expensive, bulky and power-hungry, confining them to hospitals. There is therefore a strong motivation to develop efficient electronics to enable a portable US platform that is small, cheap, and battery-operated. Beamforming (BF) is the most computationally expensive of 3D imaging. Both commercial [1] and research [2] imagers have dealt with the challenge by reducing the number of receive channels, hence simplifying the computation through the usage of far fewer elements. This comes at the cost of image quality, and the resulting machines are nonetheless still non-portable and expensive. In turn, the bottleneck of the BF process is the calculation of acoustic delays, which requires up to trillions of square roots per second. We propose a drastically more efficient architecture [3]. With geometric considerations, each delay is calculated from a small set of square roots (mapped onto CORDICs), plus two additions. In this demo, we will show the reconstruction of a 2.5M-voxel volume, supporting a transducer with 32×32 receive channels. We have fitted the architecture into a single Kintex UltraScale KU040 [4], which is unprecedented. We also extrapolated the utilization of a 80×80 instance on a Virtex UltraScale XCVU190 [4]. Table I shows the implementation results. Fig. 1 shows our beamformer custom block connected to the other FPGA subsystems. The delay calculation architecture is shown in Fig. 2. The demo setup is presented in Fig. 3, where the 3D beamformer is implemented on the FPGA, while the pre- and post-processing stages are currently performed on Matlab.

We deliver a design flow for the synthesis and convergence of application-specific networks-on-chip. The flow comes with novel features that can better address nanoscale design challenges: front-end driven floorplanning, dynamic IR-drop minimization, fast and accurate system-level power grid modeling, predictable link design. Above all, such features are addressed by different prototype engines, even from different vendors, that can be smoothly integrated into the flow by means of a common specification format called Communication Exchange Format (CEF), that enables unprecedented tool interactions. This flow is validated by means of an extensive demonstration framework.

Real-time (RT) communication support is a critical requirement for many complex embedded applications which are currently targeted to Network-on-chip (NoC) platforms. In this paper, we present novel methods to efficiently calculate worst case bandwidth and latency bounds for RT traffic streams on wormhole-switched NoCs with arbitrary topology. The proposed methods apply to best-effort NoC architectures, with no extra hardware dedicated to RT traffic support. By applying our methods to several realistic NoC designs, we show substantial improvements (more than 30 percent in bandwidth and 50 percent in latency, on average) in bound tightness with respect to existing approaches.

Reconfigurable parallel computing is required to provide high-performance embedded computing, hide hardware complexity, boost software development, and manage multiple workloads when multiple applications are running simultaneously on the emerging network-on-chip (NoC)-based multiprocessor systems-on-chip (MPSoCs) platforms. In these type of systems, the overall system performance may be affected due to congestion, and therefore parallel programming stacks must be assisted by quality-of-service (QoS) support to meet application requirements and to deal with application dynamism. In this paper, we present a hardware-software QoS-driven reconfigurable parallel computing framework, i.e., the NoC services, the runtime QoS middleware API and our ocMPI library and its tracing support which has been tailored for a distributed-shared memory ARM clustered NoC-based MPSoC platform. The experimental results show the efficiency of our software stack under a broad range of parallel kernels and benchmarks, in terms of low-latency interprocess communication, good application scalability, and most important, they demonstrate the ability to enable runtime reconfiguration to manage workloads in message-passing parallel applications.

Through silicon vias (TSVs) provide an efficient way to support vertical communication among different layers of a vertically stacked chip, enabling scalable 3-D networks-on-chip (NoC) architectures. Unfortunately, low TSV yields significantly impact the feasibility of high-bandwidth vertical connectivity. In this paper, we present a semi-automated design flow for 3-D NoCs including a defect-tolerance scheme to increase the global yield of 3-D stacked chips. Starting from an accurate physical and geometrical model of TSVs: 1) we extract a circuit-level model for vertical interconnections; 2) we use it to evaluate the design implications of extending switch architectures with ports in the vertical direction; moreover, 3) we present a defect-tolerance technique for TSV-based multi-bit links through an effective use of redundancy; and finally, 4) we present a design flow allowing for post-layout simulation of NoCs with links in all three physical dimensions. Experimental results show that a 3-D NoC implementation yields around 10% frequency improvement over a 2-D one, thanks to the propagation delay advantage of TSVs and the shorter links. In addition, the adopted fault tolerance scheme demonstrates a significant yield improvement, ranging from 66% to 98%, with a low area cost (20.9% on a vertical link in a NoC switch, which leads a modest 2.1% increase in the total switch area) in 130 nm technology, with minimal impact on very large-scale integrated design and test flows.

Research on Networks on Chips (NoCs) has spanned over a decade and its results are now visible in some products. Thus the seminal idea of using networking technology to address the chip-level interconnect problem has been shown to be correct. Moreover, as technology scales down in geometry and chips scale up in complexity, NoCs become the essential element to achieve the desired levels of performance and quality of service while curbing power consumption levels. Design and timing closure can only be achieved by a sophisticated set of tools that address NoC synthesis, optimization and validation.

In on-chip multiprocessor communication, link failures and dynamically changing application scenarios represent demanding constraints for the provision of suitable Quality of Service. Networks-on-Chip (NoCs) featuring dynamic routing are a known way to tackle these issues, but deadlock freedom and message ordering concerns arise. NoCs with configurable routing, whereby the communication routes are explicitly chosen at runtime out of a set of statically predefined alternatives, provide intelligent adaptation without impacting the consistency of traffic flows. However, configurable source routing on a NoC platform requires a design that provides fast path lookup coupled with low area and power consumption. This paper presents an exploration and synthesis approach that, depending on the required amount of routing flexibility, can for example reduce by 3 to 15 times the area cost of the NoC routing tables by adopting partially reprogrammable routing logic instead of fully reprogrammable tables. Further optimizations based on path redundancy allow to reduce up to 17 times the silicon cost.

Many Networks-on-Chip (NoC) applications exhibit one or \nmore critical traffic flows that require hard Quality of Service \n(QoS). Guaranteeing bandwidth and latency for such real time \nflows is crucial. In this paper, we present novel methods to \nefficiently calculate worst-case bandwidth and latency bounds \nand thereby provide hard QoS guarantees. Importantly, the \nproposed methods apply even to best-effort NoC architectures, \nwith no extra hardware dedicated to QoS support. By applying \nour methods to several realistic NoC designs, we show \nsubstantial improvements (on average, more than 30% in \nbandwidth and 50% in latency) in bound tightness with respect \nto existing approaches.1

The network-on-chip (NoC) interconnection paradigm has been gaining momentum thanks to its flexibility, scalability and suitability to deep submicron technology processes. The next challenge is to use NoCs as the backbones of the upcoming generation of 3D chips, assembled by stacking multiple silicon layers. Multiple technical issues have to be tackled in this respect. One of the foremost is the unsuitability of a purely synchronous design style, as it is not straightforward to impose a strict bound on the clock skew among multiple clock trees across different layers. In this paper, we present a scheme to handle mesochronous communication in 3D NoCs and analyze (i) the circuit design, (ii) the timing properties, (iii) the requirements to support flow control across mesochronous links, (iv) the implementation cost of such a scheme after placement and routing.

The design of MultiProcessor Systems-on-Chip (MPSoC) emphasizes intellectual-property (IP)-based communication-centric approaches. Therefore, for the optimization of the MPSoC interconnect, the designer must develop traffic models that realistically capture the application behavior as executing on the IP core. In this paper, we introduce a Reactive IP Emulator (RIPE) that enables an effective emulation of the IP-core behavior in multiple environments, including bit- and cycle-true simulation. The RIPE is built as a multithreaded abstract instruction-set processor, and it can generate reactive traffic patterns. We compare the RIPE models with cycle-true functional simulation of complex application behavior (task-synchronization, multitasking, and input/output operations). Our results demonstrate high-accuracy and significant speedups. Furthermore, via a case study, we show the potential use of the RIPE in a design-space-exploration context.

Several alternative building blocks have been proposed to replace planar transistors, among which a prominent spot belongs to nanometric filaments such as silicon nanowires (SiNWs) and carbon nanotubes (CNTs). However, chips leveraging these nanoscale structures are expected to be affected by a large amount of manufacturing faults, way beyond what chip architects have learned to counter. In this paper, the authors show a design flow, based on software mapping algorithms, to improve the yield of nanometric programmable logic arrays (PLAs). While further improvements to the manufacturing technology will be needed to make these devices fully usable, our flow can significantly shrink the gap between current and desired yield levels. Also, the approach does not need post-fabrication functional analysis and mapping, therefore dramatically cutting on verification costs. The authors check PLA yields by means of an accurate analyzer after Monte Carlo fault injection. The authors show that, compared to a baseline policy of wire replication, they achieve equal or better yields (8% over a set of designs) depending on the underlying defect assumptions

As embedded computing evolves towards ever more powerful architectures, the challenge of properly interconnecting large numbers of on-chip computation blocks is becoming prominent. Networks-on-chip (NoCs) have been proposed as a scalable solution to both physical design issues and increasing bandwidth demands. However, this claim has not been fully validated yet, since the design properties and tradeoffs of NoCs have not been studied in detail below the 100 nm threshold. This work is aimed at shedding light on the opportunities and challenges, both expected and unexpected, of NoC design in nanometer CMOS. We present fully working 65 nm NoC designs, a complete NoC synthesis flow and detailed scalability analysis

The ever-shrinking lithographic technologies available to chip designers enable performance and functionality breakthroughs; yet, they bring new hard problems. For example, multiprocessor systems-on-chip featuring several processing elements can be conceived, but efficiently interconnecting them while keeping the design complexity manageable is a challenge. Traditional buses are easy to deploy, but cannot provide enough bandwidth for such complex systems. A departure from legacy architectures is therefore called for. One radical path is represented by packet-switching networks-on-chip, whereas a more conservative approach interleaves bandwidth-rich components (e.g., crossbars) within the preexisting fabrics. This paper is aimed at analyzing the strengths and weaknesses of these alternative approaches by performing a thorough analysis based on actual chip floorplans after the interconnection place&route stages and after a clock tree has been distributed across the layout. Performance, area, and power results will be discussed while keeping an eye on the scalability prospects in future technology nodes

With technology scaling, the wire delay as a fraction of the total delay is increasing, and the communication architecture is becoming a major bottleneck for system performance in systems on chip (SoCs). A communication-centric design paradigm, networks on chip (NoCs), has been proposed recently to address the communication issues of SoCs. As the geometries of devices approach the physical limits of operation, NoCs will be susceptible to various noise sources such as crosstalk, coupling noise, process variations, etc. Designing systems under such uncertain conditions become a challenge, as it is harder to predict the timing behavior of the system. The use of conservative design methodologies that consider all possible delay variations due to the noise sources, targeting safe system operation under all conditions will result in poor system performance. An aggressive design approach that provides resilience against such timing errors is required for maximizing system performance. In this paper, we present T-error, which is a timing-error-tolerant aggressive design method to design the individual components of the NoC (such as switches, links, and network interfaces), so that the communication subsystem can be clocked at a much higher frequency than a traditional conservative design (up to 1.5x increase in frequency). The NoC is designed to tolerate timing errors that arise from overclocking without substantially affecting the latency for communication. We also present a way to dynamically configure the NoC between the overclocked mode and the normal mode, where the frequency of operation is lower than or equal to the traditional design's frequency, so that the error recovery penalty is completely hidden under normal operation. Experiments on several benchmark applications show large performance improvement (up to 33% reduction in average packet latency) for the proposed system when compared to traditional systems.

In recent years, increasing manufacturing density has allowed the development of Multi-Processor Systems-on-Chip (MPSoCs). Application-Specific Instruction Set Processors (ASIPs) stand out as one of the most efficient design paradigms and could be especially effective as SoC computing engines. However, multiple hurdles which are hindering the productivity of SoC designers and researchers must be solved first. Among them, the difficulty of thoroughly exploring the design space by simultaneously sweeping axes like processing elements, memory hierarchies and chip interconnect fabrics. We tackle this challenge by proposing an integrated approach where state-of-the-art platform modeling infrastructures, at the IP core level and at the system level, meet to provide the designer with maximum openness and flexibility in terms of design space exploration.

Increasing miniaturization is posing multiple challenges to electronic designers. In the context of multi-processor system-on-chips (MPSoCs), we focus on the problem of implementing efficient interconnect systems for devices which are ever more densely packed with parallel computing cores. Easily seen that traditional buses can not provide enough bandwidth, a revolutionary path to scalability is provided by packet-switched network-on-chips (NoCs), while a more conservative approach dictates the addition of bandwidth-rich components (e.g. crossbars) within the preexisting fabrics. While both alternatives have already been explored, a thorough contrastive analysis is still missing. In this paper, we bring crossbar and NoC designs to the chip layout level in order to highlight the respective strengths and weaknesses in terms of performance, area and power, keeping an eye on future scalability

With increasing communication demands of processor and memory cores in Systems on Chips (SoCs), scalable Networks on Chips (NoCs) are needed to interconnect the cores. For the use of NoCs to be feasible in today's industrial designs, a custom-tailored, application-specific NoC that satisfies the design objectives and constraints of the targeted application domain is required. In this work, we present a design methodology that automates the synthesis of such application-specific NoC architectures. We present a floorplan aware design method that considers the wiring complexity of the NoC during the topology synthesis process. This leads to detecting timing violations on the NoC links early in the design cycle and to have accurate power estimations of the interconnect. We incorporate mechanisms to prevent deadlocks during routing, which is critical for proper operation of NoCs. We integrate the NoC synthesis method with an existing design flow, automating NoC synthesis, generation, simulation and physical design processes. We also present ways to ensure design convergence across the levels. Experiments on several SoC benchmarks are presented, which show that the synthesized topologies provide a large reduction in network power consumption (2.78x on average) and improvement in performance (1.59x on average) over the best mesh and mesh-based custom topologies. An actual layout of a multimedia SoC with the NoC designed using our methodology is presented, which shows that the designed NoC supports the required frequency of operation (close to 900 MHz) without any timing violations. We could design the NoC from input specifications to layout in 4 hours, a process that usually takes several weeks.

As the geometries of the transistors reach the physical limits of operation, one of the main design challenges of systems-on-chips (SoCs) will be to provide dynamic (run-time) support against permanent and intermittent faults that can occur in the system. One of the most critical elements that affect the correct behavior of the system is the unreliable operation of on-chip memories. In this paper we present a novel solution to enable fault tolerant on-chip memory design at the system level for multimedia applications, based on the network-on-chip (NoC) interconnection paradigm. We transparently keep backup copies of critical data on a reliable memory; upon a fault event, data is fetched from the backup copy in hardware, without any software intervention. The use of a NoC backbone enables an efficient design which is modular, scalable and efficient. We proceed to demonstrating its effectiveness with two real-life application case studies, and explore the performance under varying architectural configurations. The overhead to support the proposed approach is very small compared to non-fault tolerant systems, i.e. no negative performance impact and an area increase dominated by that of just the backup storage itself.

Networks on chip (NoC) has emerged as the paradigm for designing scalable communication architecture for systems on chips (SoCs). Avoiding the conditions that can lead to deadlocks in the network is critical for using NoCs in real designs. Methods that can lead to deadlock-free operation with minimum power and area overhead are important for designing application-specific NoCs. A major class of deadlocks that occur in NoCs are due to the dependencies among the resources shared by different message types. In this work, we consider the problem of avoiding message-dependent deadlocks during the NoC topology synthesis phase. We show that by considering this issue during topology synthesis, we can obtain a significantly better NoC design than traditional methods, where the deadlock avoidance issue is dealt with separately. Our experiments on several SoC benchmarks show that our proposed scheme provides large reduction in NoC power consumption (an average of 38.5%) and NoC area (an average of 30.7%) when compared to traditional approaches

For systems-on-chip (SoC) development, a predominant part of the design time is the simulation time. Performance evaluation and design space exploration of such systems in bit- and cycle-true fashion is becoming prohibitive. We propose a traffic generation (TG) model that provides a fast and effective network-on-chip (NoC) development and debugging environment. By capturing the type and the timestamp of communication events at the boundary of an IP core in a reference environment, the TG can subsequently emulate the core's communication behavior in different environments. Access patterns and resource contention in a system are dependent on the interconnect architecture, and our TG is designed to capture the resulting reactiveness. The regenerated traffic, which represents a realistic workload, can thus be used to undertake faster architectural exploration of interconnection alternatives, effectively decoupling simulation of IP cores and of interconnect fabrics. The results with the TG on an AMBA interconnect show a simulation time speedup above a factor of 2 over a complete system simulation, with close to 100 % accuracy.

The limited scalability of current bus topologies for systems on chips (SoCs) dictates the adoption of networks on chips (NoCs) as a scalable interconnection scheme. Current SoCs are highly heterogeneous in nature, denoting homogeneous, preconfigured NoCs as inefficient drop-in alternatives. While highly parametric, fully synthesizeable (soft) NoC building blocks appear as a good match for heterogeneous MPSoC architectures, the impact of instantiation-time flexibility on performance, power and silicon cost has not yet been quantified. The paper details /spl times/pipes Lite, a design flow for automatic generation of heterogeneous NoCs. /spl times/pipes Lite is based on highly customizable, high frequency and low latency NoC modules, that are fully synthesizeable. Synthesis results provide modules that are directly comparable, if not better, than the current published state-of-the-art NoCs in terms of area, power latency and target operating frequency measurements.

Focusing on embedded applications, scratchpad memories (SPMs) look like a best-compromise solution when taking into account performance, energy consumption, and die area. The main challenge in SPM design is to optimally map memory locations to scratchpad locations. This paper describes an algorithm to solve such a mapping problem by means of dynamic programming applied to a synthesizable hardware architecture. The algorithm works by mapping segments of external memory to physically partitioned banks of an on-chip SPM; this architecture provides significant energy savings. The algorithm does not require any user-set bound on the number of partitions and takes into account partitioning overhead. Improving on previous solutions, execution time is polynomial in the number of memory locations, even in the most general solving policy. This has the major practical advantage of allowing an arbitrary number of scratchpad segments, something that was impossible with previous methods, whose running time is exponential to this number. Strategies to optimize memory requirements and speed of the algorithm are exploited. Additionally, we integrate this algorithm in a complete and automated design, simulation, and synthesis flow.

ScratchPad Memories (SPMs) are commonly used in embedded systems because they are more energy-efficient than caches and enable tighter application control on the memory hierarchy. Optimally mapping code and data to SPMs is, however, still a challenge. This paper proposes an optimal scratchpad mapping approach for code segments, which has the distinctive characteristic of working directly on application binaries, thus requiring no access to either the compiler or the application source code - a clear advantage for legacy or proprietary, IP-protected applications.The mapping problem is solved by means of a Dynamic Programming algorithm applied to the execution traces of the target application. The algorithm is able to find the optimal set of instructions blocks to be moved into a dedicated SPM, either minimizing energy consumption or execution times. A patching tool, which can use the output of the optimal mapper, modifies the binary of the application and moves the relevant portions of its code segments to memory locations inside of the SPM.

This work focuses on communication architecture analysis for multi-processor systems-on-chips (MPSoCs), and it leverages a SystemC-based platform to simulate a complete multi-processor system at the cycle-accurate and signal-accurate level. These features allow to stimulate the communication sub-system with functional traffic generated by real applications running on top of a configurable number of ARM processors. This opens up the possibility for communication infrastructure exploration and for the investigation of its impact on system performance at the highest level of accuracy. Our simulation environment proved capable of a detailed comparative analysis between two industry-standard communication architectures, under realistic workloads and different system configurations, pointing out the impact of fine grained architectural mismatches on macroscopic performance differences.

Focusing on embedded applications, scratchpad memories (SPMs) look like a best-compromise solution when taking into account performance, energy consumption and die area. The main challenge in SPM design is mapping memory locations to scratchpad locations. This paper describes an algorithm to optimally solve such a mapping problem by means of Dynamic Programming applied to a synthesizable hardware architecture. The algorithm works by mapping segments of external memory to physically partitioned banks of an on-chip SPM; this architecture provides significant energy savings. The algorithm does not require any user-set bound on the number of partitions and takes into account partitioning overhead. Improving on previous solutions, execution time is polynomial in the input size. Strategies to optimize memory requirements and speed of the algorithm are exploited. Additionally, we integrate this algorithm in a complete and automated design, simulation and synthesis flow.