1,418 research outputs found
Asynchronous techniques for system-on-chip design
SoC design will require asynchronous techniques as the large parameter variations across the chip will make it impossible to control delays in clock networks and other global signals efficiently. Initially, SoCs will be globally asynchronous and locally synchronous (GALS). But the complexity of the numerous asynchronous/synchronous interfaces required in a GALS will eventually lead to entirely asynchronous solutions. This paper introduces the main design principles, methods, and building blocks for asynchronous VLSI systems, with an emphasis on communication and synchronization. Asynchronous circuits with the only delay assumption of isochronic forks are called quasi-delay-insensitive (QDI). QDI is used in the paper as the basis for asynchronous logic. The paper discusses asynchronous handshake protocols for communication and the notion of validity/neutrality tests, and completion tree. Basic building blocks for sequencing, storage, function evaluation, and buses are described, and two alternative methods for the implementation of an arbitrary computation are explained. Issues of arbitration, and synchronization play an important role in complex distributed systems and especially in GALS. The two main asynchronous/synchronous interfaces needed in GALS-one based on synchronizer, the other on stoppable clock-are described and analyzed
A Bio-Inspired Vision Sensor With Dual Operation and Readout Modes
This paper presents a novel event-based vision sensor with two operation modes: intensity mode and spatial contrast detection. They can be combined with two different readout approaches: pulse density modulation and time-to-first spike. The sensor is conceived to be a node of an smart camera network made up of several independent an autonomous nodes that send information to a central one. The user can toggle the operation and the readout modes with two control bits. The sensor has low latency (below 1 ms under average illumination conditions), low power consumption (19 mA), and reduced data flow, when detecting spatial contrast. A new approach to compute the spatial contrast based on inter-pixel event communication less prone to mismatch effects than diffusive networks is proposed. The sensor was fabricated in the standard AMS4M2P 0.35-um process. A detailed system-level description and experimental results are provided.Office of Naval Research (USA) N00014-14-1-0355Ministerio de EconomĂa y Competitividad TEC2012- 38921-C02-02, P12-TIC-2338, IPT-2011-1625-43000
MGSim - Simulation tools for multi-core processor architectures
MGSim is an open source discrete event simulator for on-chip hardware
components, developed at the University of Amsterdam. It is intended to be a
research and teaching vehicle to study the fine-grained hardware/software
interactions on many-core and hardware multithreaded processors. It includes
support for core models with different instruction sets, a configurable
multi-core interconnect, multiple configurable cache and memory models, a
dedicated I/O subsystem, and comprehensive monitoring and interaction
facilities. The default model configuration shipped with MGSim implements
Microgrids, a many-core architecture with hardware concurrency management.
MGSim is furthermore written mostly in C++ and uses object classes to represent
chip components. It is optimized for architecture models that can be described
as process networks.Comment: 33 pages, 22 figures, 4 listings, 2 table
The Octopus switch
This chapter1 discusses the interconnection architecture of the Mobile Digital Companion. The approach to build a low-power handheld multimedia computer presented here is to have autonomous, reconfigurable modules such as network, video and audio devices, interconnected by a switch rather than by a bus, and to offload as much as work as possible from the CPU to programmable modules placed in the data streams. Thus, communication between components is not broadcast over a bus but delivered exactly where it is needed, work is carried out where the data passes through, bypassing the memory. The amount of buffering is minimised, and if it is required at all, it is placed right on the data path, where it is needed. A reconfigurable internal communication network switch called Octopus exploits locality of reference and eliminates wasteful data copies. The switch is implemented as a simplified ATM switch and provides Quality of Service guarantees and enough bandwidth for multimedia applications. We have built a testbed of the architecture, of which we will present performance and energy consumption characteristics
Modular Acquisition and Stimulation System for Timestamp-Driven Neuroscience Experiments
Dedicated systems are fundamental for neuroscience experimental protocols
that require timing determinism and synchronous stimuli generation. We
developed a data acquisition and stimuli generator system for neuroscience
research, optimized for recording timestamps from up to 6 spiking neurons and
entirely specified in a high-level Hardware Description Language (HDL). Despite
the logic complexity penalty of synthesizing from such a language, it was
possible to implement our design in a low-cost small reconfigurable device.
Under a modular framework, we explored two different memory arbitration schemes
for our system, evaluating both their logic element usage and resilience to
input activity bursts. One of them was designed with a decoupled and latency
insensitive approach, allowing for easier code reuse, while the other adopted a
centralized scheme, constructed specifically for our application. The usage of
a high-level HDL allowed straightforward and stepwise code modifications to
transform one architecture into the other. The achieved modularity is very
useful for rapidly prototyping novel electronic instrumentation systems
tailored to scientific research.Comment: Preprint submitted to ARC 2015. Extended: 16 pages, 10 figures. The
final publication is available at link.springer.co
A scalable multi-core architecture with heterogeneous memory structures for Dynamic Neuromorphic Asynchronous Processors (DYNAPs)
Neuromorphic computing systems comprise networks of neurons that use
asynchronous events for both computation and communication. This type of
representation offers several advantages in terms of bandwidth and power
consumption in neuromorphic electronic systems. However, managing the traffic
of asynchronous events in large scale systems is a daunting task, both in terms
of circuit complexity and memory requirements. Here we present a novel routing
methodology that employs both hierarchical and mesh routing strategies and
combines heterogeneous memory structures for minimizing both memory
requirements and latency, while maximizing programming flexibility to support a
wide range of event-based neural network architectures, through parameter
configuration. We validated the proposed scheme in a prototype multi-core
neuromorphic processor chip that employs hybrid analog/digital circuits for
emulating synapse and neuron dynamics together with asynchronous digital
circuits for managing the address-event traffic. We present a theoretical
analysis of the proposed connectivity scheme, describe the methods and circuits
used to implement such scheme, and characterize the prototype chip. Finally, we
demonstrate the use of the neuromorphic processor with a convolutional neural
network for the real-time classification of visual symbols being flashed to a
dynamic vision sensor (DVS) at high speed.Comment: 17 pages, 14 figure
Master of Science
thesisIntegrated circuits often consist of multiple processing elements that are regularly tiled across the two-dimensional surface of a die. This work presents the design and integration of high speed relative timed routers for asynchronous network-on-chip. It researches NoC's efficiency through simplicity by directly translating simple T-router, source-routing, single-flit packet to higher radix routers. This work is intended to study performance and power trade-offs adding higher radix routers, 3D topologies, Virtual Channels, Accurate NoC modeling, and Transmission line communication links. Routers with and without virtual channels are designed and integrated to arrayed communication networks. Furthermore, the work investigates 3D networks with diffusive RC wires and transmission lines on long wrap interconnects
Application of bus emulation techniques to the design of a PCI/MC68000 bridge
Bridges easy the interconnection and communication of devices that operate using different buses. In fact, we can see a computer as a
hierarchy of buses to which devices are connected. In this paper we design a PCI/MC68000 bridge in order to improve communications
between a Personal Computer and a MC68000 based system. The previous interface between both devices was based on the old 16-bit ISA
bus, which represented a bottleneck in their communication. However, the methodology described here is generic and can be applied to the
design of PCI bridges to other buses. We finish this work with an analysis of the bridge performance improvement which can also be easily
adapted to other situations. As an example our interface is used in an interesting situation, i.e., updating the obsolete control unit of a highly
valuable system (an industrial robot)
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Design and performance optimization of asynchronous networks-on-chip
As digital systems continue to grow in complexity, the design of conventional synchronous systems is facing unprecedented challenges. The number of transistors on individual chips is already in the multi-billion range, and a greatly increasing number of components are being integrated onto a single chip. As a consequence, modern digital designs are under strong time-to-market pressure, and there is a critical need for composable design approaches for large complex systems.
In the past two decades, networks-on-chip (NoCâs) have been a highly active research area. In a NoC-based system, functional blocks are first designed individually and may run at different clock rates. These modules are then connected through a structured network for on-chip global communication. However, due to the rigidity of centrally-clocked NoCâs, there have been bottlenecks of system scalability, energy and performance, which cannot be easily solved with synchronous approaches. As a result, there has been significant recent interest in combing the notion of asynchrony with NoC designs. Since the NoC approach inherently separates the communication infrastructure, and its timing, from computational elements, it is a natural match for an asynchronous paradigm. Asynchronous NoCâs, therefore, enable a modular and extensible system composition for an âobject-orientâ design style.
The thesis aims to significantly advance the state-of-art and viability of asynchronous and globally-asynchronous locally-synchronous (GALS) networks-on-chip, to enable high-performance and low-energy systems. The proposed asynchronous NoCâs are nearly entirely based on standard cells, which eases their integration into industrial design flows. The contributions are instantiated in three different directions.
First, practical acceleration techniques are proposed for optimizing the system latency, in order to break through the latency bottleneck in the memory interfaces of many on-chip parallel processors. Novel asynchronous network protocols are proposed, along with concrete NoC designs. A new concept, called âmonitoring networkâ, is introduced. Monitoring networks are lightweight shadow networks used for fast-forwarding anticipated traffic information, ahead of the actual packet traffic. The routers are therefore allowed to initiate and perform arbitration and channel allocation in advance. The technique is successfully applied to two topologies which belong to two different categories â a variant mesh-of-trees (MoT) structure and a 2D-mesh topology. Considerable and stable latency improvements are observed across a wide range of traffic patterns, along with moderate throughput gains.
Second, for the first time, a high-performance and low-power asynchronous NoC router is compared directly to a leading commercial synchronous counterpart in an advanced industrial technology. The asynchronous router design shows significant performance improvements, as well as area and power savings. The proposed asynchronous router integrates several advanced techniques, including a low-latency circular FIFO for buffer design, and a novel end-to-end credit-based virtual channel (VC) flow control. In addition, a semi-automated design flow is created, which uses portions of a standard synchronous tool flow.
Finally, a high-performance multi-resource asynchronous arbiter design is developed. This small but important component can be directly used in existing asynchronous NoCâs for performance optimization. In addition, this standalone design promises use in opening up new NoC directions, as well as for general use in parallel systems. In the proposed arbiter design, the allocation of a resource to a client is divided into several steps. Multiple successive client-resource pairs can be selected rapidly in pipelined sequence, and the completion of the assignments can overlap in parallel.
In sum, the thesis provides a set of advanced design solutions for performance optimization of asynchronous and GALS networks-on-chip. These solutions are at different levels, from network protocols, down to router- and component-level optimizations, which can be directly applied to existing basic asynchronous NoC designs to provide a leap in performance improvement
Core interface optimization for multi-core neuromorphic processors
Hardware implementations of Spiking Neural Networks (SNNs) represent a
promising approach to edge-computing for applications that require low-power
and low-latency, and which cannot resort to external cloud-based computing
services. However, most solutions proposed so far either support only
relatively small networks, or take up significant hardware resources, to
implement large networks. To realize large-scale and scalable SNNs it is
necessary to develop an efficient asynchronous communication and routing fabric
that enables the design of multi-core architectures. In particular the core
interface that manages inter-core spike communication is a crucial component as
it represents the bottleneck of Power-Performance-Area (PPA) especially for the
arbitration architecture and the routing memory. In this paper we present an
arbitration mechanism with the corresponding asynchronous encoding pipeline
circuits, based on hierarchical arbiter trees. The proposed scheme reduces the
latency by more than 70% in sparse-event mode, compared to the state-of-the-art
arbitration architectures, with lower area cost. The routing memory makes use
of asynchronous Content Addressable Memory (CAM) with Current Sensing
Completion Detection (CSCD), which saves approximately 46% energy, and achieves
a 40% increase in throughput against conventional asynchronous CAM using
configurable delay lines, at the cost of only a slight increase in area. In
addition as it radically reduces the core interface resources in multi-core
neuromorphic processors, the arbitration architecture and CAM architecture we
propose can be also applied to a wide range of general asynchronous circuits
and systems
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