Most network routers and switches provide some protection against the network attacks. However, the rapidly increasing amount of damages reported over the past few years indicates the urgent need for tougher security. Deep-packet inspection is one of the solutions to capture packets that can not be identified using the traditional methods. It uses a list of signatures to scan the entire content of the packet, providing the means to filter harmful packets out of the network. Since one signature does not depend on the other, the filtering process has a high degree of parallelism. Most software and hardware deep-packet filters that are in use today execute the tasks under Von Neuman architecture. Such architecture can not fully take advantage of the parallelism. For instance, one of the most widely used network intrusion-detection systems, Snort, configured with 845 patterns, running on a dual 1-GHz Pentium III system, can sustain a throughput of only 50 Mbps. The poor performance is because of the fact that the processor is programmed to execute several tasks sequentially instead of simultaneously. We designed scalable deep-packet filters on field-programmable gate arrays (FPGAs) to search for all data-independent patterns simultaneously. With FPGAs, we have the ability to reprogram the filter when there are any changes to the signature set. The smallest full-pattern matcher implementation for the latest Snort NIDS fits in a single 400k Xilinx FPGA (Spartan 3-XC3S400) with a sustained throughput of 1.6 Gbps. Given a larger FPGA, the design can scale linearly to support a greater number of patterns, as well as higher data throughput.

The Network Processor market is one of the fastest growing segments of the microprocessor industry today. In spite of this increasing market importance, there does not exist a common framework to compare the performance of different Network Processor designs. Our primary goal in this study is to fill this gap by creating the NetBench benchmarking suite. NetBench is designed to represent Network Processor workloads. It contains 11 programs that form 18 different applications. The programs are selected from all levels of packet processing: Small, low-level code fragments as well as large application-level programs are included in the suite. These applications are representative of the Network Processor applications in the market. Using the SimpleScalar simulator to model an ARM processor, we study these programs in detail and compare key characteristics, such as instructions per cycle, instruction distribution, cache behavior, and branch prediction accuracy with the programs from MediaBench. Using statistical analysis, we show that the simulation results for the programs in NetBench have significantly different characteristics than programs in MediaBench. Finally, we present performance measurements from Intel IXP1200 Network Processor to show how NetBench can be utilized.

It has been estimated that computer network worms and virus caused the loss of over $55B in 2003. Network security system use techniques such as deep packet inspection to detect the harmful packets. While software intrusion detection system running on general purpose processors can be updated in response to new attacks. They lack the processing power to monitor gigabit networks. We present a high performance pattern matching co-processor architecture that can be used to monitor and identify a large number of intrusion signature. The design consists of a bank of pattern matchers that are used to implement a highly concurrent filter. The pattern matchers can be programmed to match multiple patterns of various lengths, and are able to leverage the existing databases of threat signatures. We have been able to program the filters to match all the payload patterns defined in the widely used Snort network intrusion detection system at a rate above 7 Gbps, with memory space left to accommodate threat signatures that become available in the future.

Due to increasing number of network worms and virus, many computer network users are vulnerable to attacks. Unless network security systems use more advanced methods of content filtering such as deep packet inspection, the problem get worse. However, searching for patterns at multiple offsets in entire content of network packet requires more processing power than most general purpose processor can provide. Thus, researchers have developed high performance parallel deep packet filters for reconfigurable devices. Although some reconfigurable systems can be generated automatically from pattern database, obtaining high performance result from each subsequent reconfiguration can be a time consuming process. We present a novel architecture for programmable parallel pattern matching coprocessor. By combining a scalable coprocessor with the compact reconfigurable filter, we produce a hybrid system that is able to update the rules immediate during the time the new filter is being compiled. We mapped our hybrid filter for the latest Snort rule set on January 13, 2005, containing 2,044 unique patterns byte make up 32,384 bytes, onto a single Xilinx Virtex 4LX-XC4VLX15 FPGA with a filtering rate of 2 Gbps.

Searching for multiple string patterns in a stream of data is a computationally expensive task. The speed of the search pattern module determines the overall performance of deep packet inspection firewalls, intrusion detection systems (IDS), and intrusion prevention systems (IPS). For example, one open source IDS configured for 845 patterns, can sustain a throughput of only 50 Mbps running on a dual 1-GHz Pentium III system. Using such systems would not be practical for filtering high speed networks with over 1 Gbps traffic. Some of these systems are implemented with field programmable gate arrays (FPGA) so that they are fast and programmable. However, such FPGA filters tend to be too large to be mapped on to a single FPGA. By sharing the common sublogic in the design, we can effectively shrink the footprint of the filter. Then, for a large subset of the patterns, the logic area can be further reduced by using a memory based architecture. These design methods allow our filter for 2064 attack patterns to map onto a single Xilinx Spartan 3-XC3S2000 FPGA with a filtering rate of over 3 Gbps of network traffic.

As the performance gap between the processor cores and the memory subsystem increases, designers are forced to develop new latency hiding techniques. Arguably, the most common technique is to utilize multi-level caches. Each new generation of processors is equipped with higher levels of memory hierarchy with increasing sizes at each level. In this paper, we propose 5 different techniques that will reduce the data access times and power consumption in processors with multi-level caches. Using the information about the blocks placed into and replaced from the caches, the techniques quickly determine whether an access at any cache level will be a miss. The accesses that are identified to miss are aborted. The structures used to recognize misses are much smaller than the cache structures. Consequently the data access times and power consumption are reduced. Using the SimpleScalar simulator, we study the performance of these techniques for a processor with 5 cache levels. The best technique is able to abort 53.1% of the misses on average in SPEC2000 applications. Using these techniques, the execution time of the applications is reduced by up to 12.4% (5.4% on average), and the power consumption of the caches is reduced by as much as 11.6% (3.8% on average).

In this paper, we investigate methods for improving the hit rates in the first level of memory hierarchy. Particularly, we propose victim cache structures to reduce the number of accesses to more power consuming structures such as level 2 caches. We compare the proposed victim cache techniques to increasing the associativity or the size of the level 1 data cache and show that the enhanced victim cache technique yield better energy-delay and energy-delay-area products. We also propose techniques that predict the hit/miss behavior of the victim cache accesses and bypass the victim cache when a miss can be determined quickly. We report simulation results obtained from SimpleScalar/ARM modeling a representative Network Processor architecture. The simulations show that the victim cache is able to reduce the energy consumption by as much as 17.6 % (8.6 % on average) while reducing the execution time by as much as 8.4 % (3.7 % on average) for a set of representative applications.

We propose and evaluate a data filtering method to reduce the power consumption of high-end processors with multiple execution cores. Although the proposed method can be applied to a wide variety of multi-processor systems including MPPs, SMPs and any type of single-chip multiprocessor, we concentrate on Network Processors. The proposed method uses an execution unit called Data Filtering Engine that processes data with low temporal locality before it is placed on the system bus. The execution cores use locality to decide which load instructions have low temporal locality and which portion of the surrounding code should be off-loaded to the data filtering engine.Our technique reduces the power consumption, because a) the low temporal data is processed on the data filtering engine before it is placed onto the high capacitance system bus, and b) the conflict misses caused by low temporal data are reduced resulting in fewer accesses to the L2 cache. Specifically, we show that our technique reduces the bus accesses in representative applications by as much as 46.8% (26.5% on average) and reduces the overall power by as much as 15.6% (8.6% on average) on a single-core processor. It also improves the performance by as much as 76.7% (29.7% on average) for a processor with 16 execution cores.

In this paper, we present a flexible accelerator designed for networking applications. The accelerator can be utilized efficiently by a variety of Network Processor designs. Most Network Processors employ hardware accelerators for implementing key tasks. New applications require new tasks, such as pattern matching, to be performed on the packets in real-time. Using our proposed accelerator, we have implemented several such tasks and measured their performance. Specifically, the accelerator achieves 25-fold improvement on the performance of pattern matching, and 10-fold improvement for tree lookup, over optimized software solutions. Since the accelerator is used for different tasks, the hardware requirements are small compared to an accelerator group that implements the same set of tasks. We also present accurate analytic models to estimate the execution time of these networking tasks.

In this paper, we present an accelerator that is designed to improve performance of network processing applications, particularly layer seven networking applications. The accelerator can easily be integrated in Network Processors. We present the design details of two different FPGA implementations: a design where each task is implemented in the accelerator and another one where the accelerator must be partially reconfigured for different tasks. We also present novel algorithms for important tasks such as tree lookup and pattern matching that utilize the accelerator. We show that the accelerator improves the overall execution time by as much as 20-times for these tasks. We show that the accelerator can improve the execution time of a representative layer seven application by an order of magnitude. Finally, we discuss the effects of reconfiguration time and frequency over the performance of the accelerator.

Introduces NetBench, a benchmarking suite for network processors. NetBench contains a total of 9 applications that are representative of commercial applications for network processors. These applications are from all levels of packet processing; small, low-level code fragments as well as large application level programs are included in the suite. Using SimpleScalar simulator we study the NetBench programs in detail and characterize the network processor workloads. We also compare key characteristics such as instructions per cycle, instruction distribution, branch prediction accuracy, and cache behavior with the programs from MediaBench. Although the architectures are similar for MediaBench and NetBench suites, we show that these workloads have significantly different characteristics. Hence a separate benchmarking suite for network processors is a necessity. Finally, we present performance measurements from Intel IXP1200 Network Processor to show how NetBench can be utilized.

Digital system designs are the product of valuable effort and know-how. Their embodiments, from software and hardware description language program down to device-level netlist and mask data, represent carefully guarded intellectual property (IP). Hence, design methodologies based on IP reuse require new mechanisms to protect the rights of IP producers and owners. This paper establishes principles of watermarking-based IP protection, where a watermark is a mechanism for identification that is: (1) nearly invisible to human and machine inspection; (2) difficult to remove; and (3) permanently embedded as an integral part of the design. Watermarking addresses IP protection by tracing unauthorized reuse and making untraceable unauthorized reuse as difficult as recreating given pieces of IP from scratch. We survey related work in cryptography and design methodology, then develop desiderata, metrics, and concrete protocols for constraint-based watermarking at various stages of the very large scale integration (VLSI) design process. In particular, we propose a new preprocessing approach that embeds watermarks as constraints into the input of a black-box design tool and a new postprocessing approach that embeds watermarks as constraints into the output of a black-box design tool. To demonstrate that our protocols can be transparently integrated into existing design flows, we use a testbed of commercial tools for VLSI physical design and embed watermarks into real-world industrial designs. We show that the implementation overhead is low-both in terms of central processing unit time and such standard physical design metrics as wirelength, layout area, number of vias, and routing congestion. We empirically show that the placement and routing applications considered in our methods achieve strong proofs of authorship and are resistant to tampering and do not adversely influence timing.

As current computer-aided design (CAD) tool and very large scale integration technology capabilities create a new market of reusable digital designs, the economic viability of this new core-based design paradigm is pending on the development of techniques for intellectual property protection. This work presents the first technique that leverages the unique characteristics of field-programmable gate arrays (FPGAs) to protect commercial investment in intellectual property through fingerprinting. A hidden encrypted mark is embedded into the physical layout of a digital circuit when it is placed and routed onto the FPGA. This mark uniquely identifies both the circuit origin and original circuit recipient, yet is difficult to detect and/or remove, even via recipient collusion. While this approach imposes additional constraints on the backend CAD tools for circuit place and route, experiments indicate that the performance and area impacts are minimal.

We evaluate the validity of the fundamental assumption behind application-specific programmable processors: that applications differ from each other in key parameters which are exploitable, such as the available instruction-level parallelism (ILP), demand on various hardware resources, and the desired mix of function units. Following the tradition of the CAD community, we develop an accurate chip area estimate and a set of aggressive hardware optimization algorithms. We follow the tradition of the architecture community by using comprehensive real-life benchmarks and production quality tools. This combination enables us to build a unique framework for system-level synthesis and to gain valuable insights about design and use of application-specific programmable processors for modern applications. We explore the application-specific programmable processor (ASSP) design space to understand the relationship between performance and area. The architecture model we used is the Hewlett Packard PA-RISC with single level caches. The system, including all memory and bus latencies, is simulated and no other specialized ALU or memory structures are being used. The experimental results reveal a number of important characteristics of the ASSP design space. For example, we found that in most cases a single programmable architecture performs similarly to a set of architectures that are tuned to individual application. A notable exception is highly cost sensitive designs, which we observe need a small number of specialized architectures that require smaller areas. Also, it is clear that there is enough parallelism in the typical media and communication applications to justify use of high number of function units. We found that the framework introduced in this paper can be very valuable in making early design decisions such as area and architectural configuration tradeoff, cache and issue width tradeoff under area constraint, and the number of branch units and issue width.

Article Free Access Share on Offline program re-mapping to improve branch prediction efficiency in embedded systems Authors: Stephen S. Brown The Department of Electrical Engineering, The University of California, Los Angeles The Department of Electrical Engineering, The University of California, Los AngelesView Profile , Jeet Asher The Department of Electrical Engineering, The University of California, Los Angeles The Department of Electrical Engineering, The University of California, Los AngelesView Profile , William H. Mangione-Smith The Department of Electrical Engineering, The University of California, Los Angeles The Department of Electrical Engineering, The University of California, Los AngelesView Profile Authors Info & Claims ASP-DAC '00: Proceedings of the 2000 Asia and South Pacific Design Automation ConferenceJanuary 2000 Pages 111–116https://doi.org/10.1145/368434.368588Online:28 January 2000Publication History 2citation66DownloadsMetricsTotal Citations2Total Downloads66Last 12 Months3Last 6 weeks1 Get Citation AlertsNew Citation Alert added!This alert has been successfully added and will be sent to:You will be notified whenever a record that you have chosen has been cited.To manage your alert preferences, click on the button below.Manage my Alerts New Citation Alert!Please log in to your account Save to BinderSave to BinderCreate a New BinderNameCancelCreateExport CitationPublisher SiteeReaderPDF

Article A technique for QoS-based system partitioning Share on Authors: Johnson S. Kin Electrical Engineering Department, University of California at Los Angeles, Los Angeles, CA Electrical Engineering Department, University of California at Los Angeles, Los Angeles, CAView Profile , Chunho Lee Computer Science Department, University of California at Los Angeles, Los Angeles, CA Computer Science Department, University of California at Los Angeles, Los Angeles, CAView Profile , William H. Mangione-Smith Electrical Engineering Department, University of California at Los Angeles, Los Angeles, CA Electrical Engineering Department, University of California at Los Angeles, Los Angeles, CAView Profile , Miodrag Potkonjak Computer Science Department, University of California at Los Angeles, Los Angeles, CA Computer Science Department, University of California at Los Angeles, Los Angeles, CAView Profile Authors Info & Claims ASP-DAC '00: Proceedings of the 2000 Asia and South Pacific Design Automation ConferenceJanuary 2000 Pages 241–246https://doi.org/10.1145/368434.368620Published:28 January 2000 0citation1,245DownloadsMetricsTotal Citations0Total Downloads1,245Last 12 Months0Last 6 weeks0 Get Citation AlertsNew Citation Alert added!This alert has been successfully added and will be sent to:You will be notified whenever a record that you have chosen has been cited.To manage your alert preferences, click on the button below.Manage my AlertsNew Citation Alert!Please log in to your account Save to BinderSave to BinderCreate a New BinderNameCancelCreateExport CitationPublisher SiteGet Access

Simulations for modern designs are often performed on Field Programmable Gate Array technology in a functional test and debugging process known as emulation, allowing for more complex simulations than possible in software. One drawback to emulation is the lengthy time spent in the back-end CAD tools for each debugging iteration, including debugging changes and the introduction of control and observation logic. We have developed a technique that confines the re-place-and-route area to only the portions of the design affected by the introduction of the test logic and by the debugging changes. Therefore, the back-end CAD effort for error detection, localization, and correction is reduced. This benefit is achieved by partitioning the design at the physical level into independent blocks, and the test logic and design changes are localized to the affected blocks. The result is a shortened time between debugging iterations, and thus a shortened time-to-market for the design.

Most advanced forms of security for electronic transactions rely on the public-key cryptosystems developed by Rivest, Shamir and Adleman. Unfortunately, these systems are only secure while it remains difficult to factor large integers. The fastest published algorithms for factoring large numbers have a common sieving step. These sieves collect numbers that are completely factored by a set of prime numbers that are known in advance. Furthermore, the time required to execute these sieves currently dominates the runtime of the factoring algorithms. We show how the sieving process can be mapped to the Mojave configurable computing architecture. The mapping exploits unique properties of the sieving algorithms to fully utilize the bandwidth of a multiple bank interleaved memory system. The sieve has been mapped to a single programmable hardware unit on the Mojave computer, and achieves a clock frequency of 16 MHz. The full system implementation sieves over 28 times faster than an UltraSPARC Workstation. A simple upgrade to 8ns SRAMs will result in a speedup factor of 160.

Most modern microprocessors employ one or two levels of on-chip caches in order to improve performance. Caches typically are implemented with static RAM cells and often occupy a large portion of the chip area. Not surprisingly, these caches can consume a significant amount of power. In many applications, such as portable devices, energy efficiency is more important than performance. We propose sacrificing some performance in exchange for energy efficiency by filtering cache references through an unusually small first level cache. We refer to this structure as the filter cache. A second level cache, similar in size and structure to a conventional first level cache, is positioned behind the filter cache and serves to mitigate the performance loss. Extensive experiments indicate that a small filter cache still can achieve a high hit rate and good performance. This approach allows the second level cache to be in a low power mode most of the time, thus resulting in power savings. The filter cache is particularly attractive in low power applications, such as the embedded processors used for communication and multimedia applications. For example, experimental results across a wide range of embedded applications show that a direct mapped 255-byte filter cache achieves a 58 percent power reduction while reducing performance by 21 percent. This trade-off results in a 51 percent reduction in the energy-delay product when compared to a conventional design.

The expanded use of field programmable gate arrays (FPGA) in remote, long life, and system-critical applications requires the development and implementation of effective, efficient FPGA fault-tolerance techniques. FPGA have inherent redundancy and in-the-field reconfiguration capabilities, thus providing alternatives to standard integrated circuit redundancy-based fault-recovery techniques. Runtime reliability can be enhanced by using such unique features. Recovery from permanent logic and interconnect faults without runtime computer-aided design (CAD) support can be efficiently performed with the use of fine-grained and physical design partitioning. Faults are localized to small partitioned blocks that have fixed interfaces to the surrounding portions of the design, and the affected blocks are reconfigured with previously generated, functionally equivalent block instances that do not use the faulty resources. This technique minimizes the post-fault-detection system downtime, while requiring little area overhead. Only the finely located faulty portions of the FPGA are removed from use. In addition, the end user need not have access to CAD tools, making the algorithm completely transparent to system users. This approach has been efficiently implemented on a diverse set of FPGA architectures. The algorithm's flexibility is also apparent from the variable emphases that can be placed on system reliability, area overhead, timing overhead, design effort, and system memory. Given user-defined emphases, the algorithm can be modified to specific application requirements. Experiments using random s-independent and s-correlated fault models reveal that the approach enhances system reliability, while minimizing area and timing overhead.

Article Power efficient mediaprocessors: design space exploration Share on Authors: Johnson Kin Department of Electrical Enginerring, UCLA Department of Electrical Enginerring, UCLAView Profile , Chunho Lee Department of Computer Science, UCLA Department of Computer Science, UCLAView Profile , William H. Mangione-Smith Department of Electrical Enginerring, UCLA Department of Electrical Enginerring, UCLAView Profile , Miodrag Potkonjak Department of Computer Science, UCLA Department of Computer Science, UCLAView Profile Authors Info & Claims DAC '99: Proceedings of the 36th annual ACM/IEEE Design Automation ConferenceJune 1999 Pages 321–326https://doi.org/10.1145/309847.309943Published:01 June 1999 11citation528DownloadsMetricsTotal Citations11Total Downloads528Last 12 Months2Last 6 weeks0 Get Citation AlertsNew Citation Alert added!This alert has been successfully added and will be sent to:You will be notified whenever a record that you have chosen has been cited.To manage your alert preferences, click on the button below.Manage my AlertsNew Citation Alert!Please log in to your account Save to BinderSave to BinderCreate a New BinderNameCancelCreateExport CitationPublisher SiteGet Access

A number of researchers have proposed using digital marks to provide ownership identification for intellectual property. Many of these techniques share three specific weaknesses: complexity of copy detection, vulnerability to mark removal after revelation for ownership verification, and mark integrity issues due to partial mark removal. This paper presents a method for watermarking field programmable gate array (FPGA) intellectual property (IP) that achieves robustness by responding to these three weaknesses. The key technique involves using secure hash functions to generate and embed multiple small marks that are more detectable, verifiable, and secure than existing IP protection techniques.

No abstract available.

Many previous attempts at ASIP (application-specific instruction set processor) synthesis have employed template matching techniques to target function units to application code, or directly design new units to extract maximum performance. This paper presents an entirely new approach to specializing hardware for application-specific needs. In our framework of a parameterized VLIW processor, we use a post-modulo scheduling analysis to reduce the allocated hardware resources while increasing the code's performance. Initial results indicate significant savings in area, as well as optimizations to increase FIR filter code performance by 200% to 300%.

Distributed hypermedia system that supports collaboration is an emerging platform for creation, discovery, management and delivery of information.We present an approach to low power system design space exploration for distributed hypermedia applications.Traditionally, low power design and synthesis of application specific programmable processors has been done in the context of a given number of operations required to complete a task.Our approach utilizes the modem advances in compiler technology and architectural enhancements that are well matched to the compiler technology.This work is, to the best of our knowledge, the first attempt to address the need for synthesis of low power hypermedia processors.Also, this is the first work to address the power efficiency through exploiting instruction level parallelism (ILP) found in hypermedia tasks by an production quality ILP compiler.Using the developed framework we conduct an extensive exploration of low power system design space for a hypermedia application under area and throughput constraints.The framework introduced in this paper is very valuable in making early low power design decisions such as architectural configuration trade-offs including the cache and issue width trade-off under area and throughput constraint, and the number of branch units and issue width.

Due to the increasing popularity of multimedia and communications applications, requirements for application-specific systems typically include design flexibility and data management ability. Since the development of such systems is a market-driven task, reducing the time to market and manufacturing cost, while still satisfying application performance requirements, is an important system synthesis requirement. We have developed a new approach for area optimization of core-based systems. The approach uses basic block relocation in order to reduce the number of cache misses and, thus, enable hardware savings during system synthesis. Given a processor model, a cache model, and a set of nonpreemptive tasks with timing constraints, the goal of the synthesis framework is to select a system configuration (processor, I-cache, and D-cache) of minimal area that satisfies the performance constraints. The system synthesis framework has two key components. The first component is a code optimization engine that relocates basic blocks within a given assembly program in order to reduce the number of cache misses. The second component is a search mechanism that leverages the improvements in code performance obtained by the first component to select the most area-efficient system configuration. In order to bridge the gap between the profiling and modeling tools, we have constructed a new performance evaluation platform. It integrates the existing modeling, profiling, and simulation tools with the developed system-level synthesis tools. The effectiveness of the synthesis approach is demonstrated on a variety of modern real-life multimedia and communication applications.

We developed a new modular synthesis approach for design of low-power core-based data-intensive application-specific systems on silicon. The power optimization is conducted in three steps: minimization of instruction cache misses, placement of frequently executed sequential basic blocks of code in consecutive Gray code addressed memory locations, and processor and cache application-driven selection for low power. In order to bridge the gap between the profiling and modeling tools from the two traditionally disjoint synthesis domains (architecture and CAD), we developed a new synthesis and evaluation platform. The platform integrates the existing modeling, profiling, and simulation tools with the developed system-level synthesis tools. The effectiveness of the approach is demonstrated on a variety of modern industrial-strength multimedia and communication applications.

Digital system designs are the product of valuable effort and knowhow. Their embodiments, from software and HDL program down to device-level netlist and mask data, represent carefully guarded intellectual property (IP). Hence, design methodologies based on IP reuse require new mechanisms to protect the rights of IP producers and owners. This paper establishes principles of watermarkingbased IP protection, where a watermark is a mechanism for identification that is (i) nearly invisible to human and machine inspection, (ii) difficult to remove, and (iii) permanently embedded as an integral part of the design. We survey related work in cryptography and design methodology, then develop desiderata, metrics and example approaches -- centering on constraint-based techniques -- for watermarking at various stages of the VLSI design process. 1 Introduction The advance of processing technology has led to a rapid increase in IC design complexity. The economic drivers are compelling: only by put...

In this paper we report a framework that makes it possible for a designer to rapidly explore the application-specific programmable processor design space under area constraints. The framework uses a production-quality compiler and simulation tools to synthesize a high performance machine for an application. Using the framework we evaluate the validity of the fundamental assumption behind the development of application-specific programmable processors. Application-specific processors are based on the idea that applications differ from each other in key architectural parameters, such as the available instruction-level parallelism, demand on various hardware components (e.g. cache memory units, register files) and the need for different number of functional units. We found that the framework introduced in this paper can be valuable in making early design decisions such as area and architectural trade-off, cache and instruction issue width trade-off under area constraint, and the number of branch units and issue width.

Optimization and query problems provide the best clear opportunity for configurable computing systems to achieve a significant performance advantage over ASICs. Programmable hardware can be optimized to solve a specific problem instance that only needs to be solved once, and the circuit can be thrown away after its single execution. This paper investigates the applicability of this technology to solving a specific query problem, known as Boolean Satisfiability. We provide a system for capturing the complete execution cost of this approach, by accounting for CAD tool execution time. The key to this approach is to circumvent the standard CAD tools and directly generate circuits at runtime. A set of example circuits is presented as part of the system evaluation, and a complete implementation on the Xilinx XC6216 FPGA is presented.

While system reliability is conventionally achieved through component replication, we have developed a fault-tolerance approach for FPGA-based systems that comes at a reduced cost in terms of design time, volume, and weight. We partition the physical design into a set of tiles. In response to a component failure, we capitalize on the unique reconfiguration capabilities of FPGAs and replace the affected tile with a functionally equivalent tile that does not rely on the faulty component. Unlike fixed structure fault-tolerance techniques for ASICs and microprocessors, this approach allows a single physical component to provide redundant backup for several types of components. Experimental results conducted on a subset of the MCNC benchmarks demonstrate a high level of realiability with low timing and hardware overhead.

Abstract – This work presents the first known attempt to leverage the unique characteristics of FPGAs to protect commercial investments in intellectual property. A watermark is applied to the physical layout of a digital circuit when it is mapped into an FPGA. This watermark uniquely identifies the circuit origin and yet is difficult to detect. While this approach imposes additional constraints, experiments involving a number of large complex designs indicate that the performance impact is small. 1

We present a framework for area optimal system design space exploration for hypermedia applications. We focus on a category of processors that are programmable yet optimized to a hypermedia application. The key components of the framework presented in this paper are a retargetable instruction-level parallelism compiler, instruction level simulators, a set of complete media applications written in a high level language and a media processor synthesis algorithm. The framework addresses the need for area optimal system design by exploiting the instruction-level parallelism found in media applications by compilers that target multiple-instruction-issue processors. Using the framework we conduct an extensive exploration of area optimal system design space for a hypermedia application. We found that there is enough ILP in the typical media and communication applications to achieve highly concurrent execution when throughput requirements are high. On the other hand, when throughput requirements are low, there is no need to use multiple-instruction-issue processors.

Under the Mojave configurable computing project, we have developed a system for achieving high performance on an automatic target recognition (ATR) application through the use of configurable computing technology. The ATR system studied here involves real-time image acquisition from a synthetic aperture radar (SAR). SAR images exhibit statistical properties which can be used to improve system performance. In this paper, the Mojave configurable computing system uses field programmable gate arrays (FPGA's) to implement highly specialized circuits while retaining the flexibility of programmable components. A controller sequences through a set of specialized circuits in response to real-time events. Computer-aided design (CAD) tools have been developed to support the automatic generation of these specialized circuits. The resulting configurable computing system achieves a significant performance advantage over the existing solution, which is based on application specific integrated circuit (ASIC) technology.

Fault-tolerance is an important system metric for many operating environments, from automotive to space exploration. The conventional technique for improving system reliability is through component replication, which usually comes at significant cost: increased design time, testing, power consumption, volume, and weight. We have developed a new fault-tolerance approach that capitalizes on the unique reconfiguration capabilities of field programmable gate arrays (FPGA's). The physical design is partitioned into a set of tiles. In response to a component failure, a functionally equivalent tile that does not rely on the faulty component replaces the affected tile. Unlike application specific integrated circuit (ASIC) and microprocessor design methods, which result in fixed structures, this technique allows a single physical component to provide redundant backup for several types of components. Experimental results conducted on a subset of the MCNC benchmarks demonstrate a high level of reliability with low timing and hardware overhead.

We introduce a technique for on-line built-in self-testing (BIST) of bus-based field programmable gate arrays (FPGAs). This system detects deviations from the intended functionality of an FPGA without using special-purpose hardware, hardware external to the device, and without interrupting system operation. Such a system would be useful for mission-critical applications with resource constraints. The system solves these problems through an on-line fault scanning methodology. A device's internal resources are configured to test for faults. Testing scans across an FPGA, checking a section at a time. Simulation on a model FPGA supports the viability and effectiveness of such a system.

We developed a new hierarchical modular approach for synthesis of area-minimal core-based data-intensive systems. The optimization approach employs a novel global least-constraining most-constrained heuristic to minimize the instruction cache misses for a given application, instruction cache size and organization. Based on this performance optimization technique, we constructed a strategy to search for a minimal area processor core, and an instruction and data cache which satisfy the performance characteristics of a set of target applications. The synthesis platform integrates the existing modeling, profiling, and simulation tools with the developed system-level synthesis tools. The effectiveness of the approach is demonstrated on a variety of modern real-life multimedia and communication applications.

Most modern microprocessors employ one or two levels of on-chip caches in order to improve performance. These caches are typically implemented with static RAM cells and often occupy a large portion of the chip area. Not surprisingly, these caches often consume a significant amount of power. In many applications, such as portable devices, low power is more important than performance. We propose to trade performance for power consumption by filtering cache references through an unusually small L1 cache. An L2 cache, which is similar in size and structure to a typical L1 cache, is positioned behind the filter cache and serves to reduce the performance loss. Experimental results across a wide range of embedded applications show that the filter cache results in improved memory system energy efficiency. For example, a direct mapped 256-byte filter cache achieves a 58% power reduction while reducing performance by 21%, corresponding to a 51% reduction in the energy-delay product over conventional design.

Cost and power consumption are two of the most important design factors for many embedded systems, particularly consumer devices. Products such as personal digital assistants, pagers with integrated data services and smart phones have fixed performance requirements but unlimited appetites for reduced cost and increased battery life. Program compression is one technique that can be used to attack both of these problems. Compressed programs require less memory, thus reducing the cost of both direct materials and manufacturing. Furthermore, by relying on compressed memory, the total number of memory references is reduced. This reduction saves power by lowering the traffic on high-capacitance buses. This paper discusses a new approach to implementing transparent program compression that requires little or no hardware support. Procedures are compressed individually, and a directory structure is used to bind them together at run-time. Decompressed procedures are explicitly cached in ordinary RAM as complete units, thus resolving references within each procedure. This approach has been evaluated on a set of 25 embedded multimedia and communications applications, and results in an average memory reduction of 40% with a run-time performance overhead of 10%.

Significant advances have been made in compilation technology for capitalizing on instruction-level parallelism (ILP). The vast majority of ILP compilation research has been conducted in the context of general-purpose computing, and more specifically the SPEC benchmark suite. At the same time, a number of microprocessor architectures have emerged which have VLIW and SIMD structures that are well matched to the needs of the ILP compilers. Most of these processors are targeted at embedded applications such as multimedia and communications, rather than general-purpose systems. Conventional wisdom, and a history of hand optimization of inner-loops, suggests that ILP compilation techniques are well suited to these applications. Unfortunately, there currently exists a gap between the compiler community and embedded applications developers. This paper presents MediaBench, a benchmark suite that has been designed to fill this gap. This suite has been constructed through a three-step process: intuition and market driven initial selection, experimental measurement to establish uniqueness, and integration with system synthesis algorithms to establish usefulness.

UCLA has constructed a network testbed which serves as an environment for developing wireless multimedia systems. The first generation testbed consists of a set of battery powered terminals with low-bit rate video codecs connected to a peer-to-peer multi-hop network over spread spectrum radios. Not surprisingly, this set of features draws considerable current during operation, and achieves a battery life of approximately one hour using a 24 Wh NiMH battery. This report discusses the power consumption of the existing testbed, lessons learned during its development, and a course of action directed to improving battery life for a portable multimedia terminal. The key advancement is the development of a complete system architecture focused on turning off power to components and subsystems. Starting with communications protocols, and progressing up through processors to APIs, this new design extends useful battery life through a significant reduction in current drain.

Several commercial processors, including the Motorola 88110 and the DEC Alpha, are capable of issuing multiple operations per clock cycle. Optimization of the pipeline depth and number of function units in these processors has been largely ignored due to limited semiconductor resources. Recently, advances in feature size and packaging technologies have removed these limitations. It is possible that next-generation processor designs may benefit from multiple function unit copies and optimize pipeline depths. The paper investigates the feasibility of performing synthesis at the architectural specification level. The design space is optimized for performance constrained by a hardware model of silicon area. The results of this study indicate that cost-effective high performance can be achieved with the addition of small amounts of function unit duplication. These results are also used to comment on the validity of the "benchmark suite" approach to performance evaluation and machine design.>

A performance bounding methodology that explains the performance of loop-dominated scientific applications on particular systems is presented. The throughput of key hardware units that are common bottlenecks in concurrent machines is modeled. A workload characterization is proposed, and upper bounds on the performance of specific machine-workload pairs are derived. Comparing delivered performance with bounds focuses attention on areas for improvement and indicates how much improvement might be attainable. A detailed analysis and performance improvement effort for the IBM RS/6000 produced an average lower bound of 1.27 clocks per floating-point operation (CPF), whereas machine peak performance is 0.5 CPF and the V2.01 Fortran compiler attains only 2.43 CPF. Code improvements in this study have achieved 1.36 CPF, increasing the harmonic mean steady-state inner loop performance to 97.6% of the MFLOPS bound. Subsequently, the V2.02 compiler achieved 1.75 CPF, and 1.60 with carefully chosen preprocessing.>

To enable concurrent instruction execution, scientific computers generally rely on pipelining, which combines with faster system clocks to achieve greater throughput. Each concurrently executing instruction requires buffer space, usually implemented as a register, to receive its result. This paper focuses on the issue of how many registers are required to achieve optimal performance in pipelined scientific computers. Four machine models are considered: single, double, and triple issue scalar machines, and vector machines with various register lengths. A model is presented that accurately relates the register requirements for optimum performance cyclically scheduled loops with tree-dependence graphs to the degree of function unit pipelining, the instruction issue bandwidth, and code properties. A method for finding upper and lower bounds on the minimum register requirements is also presented.The result of this work is a theory for assessing register requirements that can be used to reveal fundamental differences among machines within a space of architectural and implementation design choices. Some experimental data is also provided to support the theory.

article Vector register design for polycyclic vector scheduling Share on Authors: William Mangione-Smith Department of Electrical Engineering and Computer Science, The University of Michigan, Ann Arbor, Michigan Department of Electrical Engineering and Computer Science, The University of Michigan, Ann Arbor, MichiganView Profile , Santosh G. Abraham Department of Electrical Engineering and Computer Science, The University of Michigan, Ann Arbor, Michigan Department of Electrical Engineering and Computer Science, The University of Michigan, Ann Arbor, MichiganView Profile , Edward S. Davidson Department of Electrical Engineering and Computer Science, The University of Michigan, Ann Arbor, Michigan Department of Electrical Engineering and Computer Science, The University of Michigan, Ann Arbor, MichiganView Profile Authors Info & Claims ACM SIGOPS Operating Systems ReviewVolume 25Issue Special IssueApr. 1991 pp 154–163https://doi.org/10.1145/106974.328664Published:01 April 1991 8citation339DownloadsMetricsTotal Citations8Total Downloads339Last 12 Months2Last 6 weeks0 Get Citation AlertsNew Citation Alert added!This alert has been successfully added and will be sent to:You will be notified whenever a record that you have chosen has been cited.To manage your alert preferences, click on the button below.Manage my AlertsNew Citation Alert!Please log in to your account Save to BinderSave to BinderCreate a New BinderNameCancelCreateExport CitationPublisher SiteGet Access