Vaughn Betz

Bio: Vaughn Betz is an academic researcher from University of Toronto. The author has contributed to research in topics: Field-programmable gate array & Programmable logic device. The author has an hindex of 37, co-authored 197 publications receiving 7322 citations. Previous affiliations of Vaughn Betz include Cameron International & University of Illinois at Urbana–Champaign.

Architecture and CAD for Deep-Submicron FPGAS

Abstract: From the Publisher: Architecture and CAD for Deep-Submicron FPGAs addresses several key issues in the design of high-performance FPGA architectures and CAD tools, with particular emphasis on issues that are important for FPGAs implemented in deep-submicron processes. Three factors combine to determine the performance of an FPGA: the quality of the CAD tools used to map circuits into the FPGA, the quality of the FPGA architecture, and the electrical (i.e. transistor-level) design of the FPGA. Architecture and CAD for Deep-Submicron FPGAs examines all three of these issues in concert.

VPR: A new packing, placement and routing tool for FPGA research

Abstract: We describe the capabilities of and algorithms used in a new FPGA CAD tool, Versatile Place and Route (VPR). In terms of minimizing routing area, VPR outperforms all published FPGA place and route tools to which we can compare. Although the algorithms used are based on previously known approaches, we present several enhancements that improve run-time and quality. We present placement and routing results on a new set of large circuits to allow future benchmark comparisons of FPGA place and route tools on circuit sizes more typical of today's industrial designs.

VTR 7.0: Next Generation Architecture and CAD System for FPGAs

Abstract: Exploring architectures for large, modern FPGAs requires sophisticated software that can model and target hypothetical devices. Furthermore, research into new CAD algorithms often requires a complete and open source baseline CAD flow. This article describes recent advances in the open source Verilog-to-Routing (VTR) CAD flow that enable further research in these areas. VTR now supports designs with multiple clocks in both timing analysis and optimization. Hard adder/carry logic can be included in an architecture in various ways and significantly improves the performance of arithmetic circuits. The flow now models energy consumption, an increasingly important concern. The speed and quality of the packing algorithms have been significantly improved. VTR can now generate a netlist of the final post-routed circuit which enables detailed simulation of a design for a variety of purposes. We also release new FPGA architecture files and models that are much closer to modern commercial architectures, enabling more realistic experiments. Finally, we show that while this version of VTR supports new and complex features, it has a 1.5× compile time speed-up for simple architectures and a 6× speed-up for complex architectures compared to the previous release, with no degradation to timing or wire-length quality.

Using cluster-based logic blocks and timing-driven packing to improve FPGA speed and density

Abstract: In 1999, most commercial FPGAs, like the Altera Flex and Xilinx Virtex FPGAs already had cluster-based logic blocks. However, the modeling and evaluation of these sorts of architectures was still in its infancy. In the previous year, Betz had shown that cluster-based logic blocks led to improved density. The real advantage of clustered-based logic blocks, though, was speed, as this paper demonstrates. In doing so, this paper opened up an entirely new research area, setting the framework for numerous packing algorithms that have become a fundamental part of any FPGA CAD flow.

Timing-driven placement for FPGAs

Abstract: In this paper we introduce a new Simulated Annealing-based timing-driven placement algorithm for FPGAs. This paper has three main contributions. First, our algorithm employs a novel method of determining source-sink connection delays during placement. Second, we introduce a new cost function that trades off between wire-use and critical path delay, resulting in significant reductions in critical path delay without significant increases in wire-use. Finally, we combine connection-based and path-based timing-analysis to obtain an algorithm that has the low time-complexity of connection-based timing-driven placement, while obtaining the quality of path-based timing-driven placement.A comparison of our new algorithm to a well known non-timing-driven placement algorithm demonstrates that our algorithm is able to increase the post-place-and-route speed (using a full path-based timing-driven router and a realistic routing architecture) of 20 MCNC benchmark circuits by an average of 42%, while only increasing the minimum wiring requirements by an average of 5%.

Reconfigurable computing: a survey of systems and software

Abstract: Due to its potential to greatly accelerate a wide variety of applications, reconfigurable computing has become a subject of a great deal of research. Its key feature is the ability to perform computations in hardware to increase performance, while retaining much of the flexibility of a software solution. In this survey, we explore the hardware aspects of reconfigurable computing machines, from single chip architectures to multi-chip systems, including internal structures and external coupling. We also focus on the software that targets these machines, such as compilation tools that map high-level algorithms directly to the reconfigurable substrate. Finally, we consider the issues involved in run-time reconfigurable systems, which reuse the configurable hardware during program execution.

VPR: A new packing, placement and routing tool for FPGA research

Abstract: We describe the capabilities of and algorithms used in a new FPGA CAD tool, Versatile Place and Route (VPR). In terms of minimizing routing area, VPR outperforms all published FPGA place and route tools to which we can compare. Although the algorithms used are based on previously known approaches, we present several enhancements that improve run-time and quality. We present placement and routing results on a new set of large circuits to allow future benchmark comparisons of FPGA place and route tools on circuit sizes more typical of today's industrial designs.

Measuring the Gap Between FPGAs and ASICs

Abstract: This paper presents experimental measurements of the differences between a 90-nm CMOS field programmable gate array (FPGA) and 90-nm CMOS standard-cell application-specific integrated circuits (ASICs) in terms of logic density, circuit speed, and power consumption for core logic. We are motivated to make these measurements to enable system designers to make better informed choices between these two media and to give insight to FPGA makers on the deficiencies to attack and, thereby, improve FPGAs. We describe the methodology by which the measurements were obtained and show that, for circuits containing only look-up table-based logic and flip-flops, the ratio of silicon area required to implement them in FPGAs and ASICs is on average 35. Modern FPGAs also contain "hard" blocks such as multiplier/accumulators and block memories. We find that these blocks reduce this average area gap significantly to as little as 18 for our benchmarks, and we estimate that extensive use of these hard blocks could potentially lower the gap to below five. The ratio of critical-path delay, from FPGA to ASIC, is roughly three to four with less influence from block memory and hard multipliers. The dynamic power consumption ratio is approximately 14 times and, with hard blocks, this gap generally becomes smaller

Measuring the gap between FPGAs and ASICs

Abstract: This paper presents experimental measurements of the differences between a 90nm CMOS FPGA and 90nm CMOS Standard Cell ASICs in terms of logic density, circuit speed and power consumption. We are motivated to make these measurements to enable system designers to make better informed hoices between these two media and to give insight to FPGA makers on the deficiencies to attack and thereby improve FPGAs. In the paper, we describe the methodology by which the measurements were obtained and we show that, for circuits containing only combinational logic and flip-flops, the ratio of silicon area required to implement them in FPGAs and ASICs is on average 40. Modern FPGAs also contain "hard" blocks such as multiplier/accumulators and block memories and we find that these blocks reduce this average area gap significantly to as little as 21. The ratio of critical path delay, from FPGA to ASIC, is roughly 3 to 4, with less influence from block memory and hard multipliers. The dynamic power onsumption ratio is approximately 12 times and, with hard blocks, this gap generally becomes smaller.

CMOL FPGA: a reconfigurable architecture for hybrid digital circuits with two-terminal nanodevices

Abstract: This paper describes a digital logic architecture for ‘CMOL’ hybrid circuits which combine a semiconductor–transistor (CMOS) stack and two levels of parallel nanowires, with molecular-scale nanodevices formed between the nanowires at every crosspoint. This cell-based, field-programmable gate array (FPGA)-like architecture is based on a uniform, reconfigurable CMOL fabric, with four-transistor CMOS cells and two-terminal nanodevices (‘latching switches’). The switches play two roles: they provide diode-like I –V curves for logic circuit operation, and allow circuit mapping on CMOL fabric and its reconfiguration around defective nanodevices. Monte Carlo simulations of two simple circuits (a 32-bit integer adder and a 64-bit full crossbar switch) have shown that the reconfiguration allows one to increase the circuit yield above 99% at the fraction of bad nanodevices above 20%. Estimates have shown that at the same time the circuits may have extremely high density (approximately 500 times higher than that of the usual CMOS FPGAs with the same design rules), while operating at higher speed at acceptable power consumption. (Some figures in this article are in colour only in the electronic version)