This study compares the speed, area, and latency of shift-and-add arithmetic implemented within fine-grained FPGA resources and within a proposed coarse-grained embedded block for FPGAs. It begins by optimizing the mapping of various shift-and-add architectures within the fine-grained resources of a commercial FPGA to determine which provides the best area, delay, and latency for various word-lengths. It then proposes a new coarse-grained block that supports 16, 32, and 64-bit shift-and-add arithmetic and finally compares coarse-grained implementations to the best fine-grained implementations. Our results show that the coarse-grain implementations are between 15 and 47 times smaller and 5 to 18 times faster, depending on the implementation.

This paper describes the acceleration of virtual ecology models using field-programmable gate arrays (FPGAs). Our approach targets models generated by the Virtual Ecology Workbench (VEW); an existing tool used by biological oceanographers to build and analyze models of the plankton ecosystem in the upper ocean. Depending on the plankton study and required level of detail, the logic, memory, and data transfer requirements of the generated models can vary significantly. Using FPGAs, hardware implementations can be customized to the specific requirements of the ecological system under study and provide significant speed-ups compared to software implementations. This paper describes a framework for maximizing the speedup of VEW generated models implemented on FPGA-based acceleration platforms and then describes the implementation of a typical VEW generated model to validate the framework and demonstrate that significant speedups are possible. Based on timing and area estimates from a commercial synthesis tool, the example model implemented on a Celoxica RCHTX acceleration board featuring a Xilinx Virtex-4 FPGA performs 39 times faster at 150 MHz than the software implementation on an AMD Opteron 2200 series CPU at 1.0 GHz.

FPGA clock networks consume a significant amount of power, since they toggle every clock cycle and must be flexible enough to implement the clocks for a wide range of different applications. The efficiency of FPGA clock networks can be improved by reducing this flexibility; however, reducing the flexibility introduces stricter constraints during the clustering and placement stages of the FPGA CAD flow. These constraints can reduce the overall efficiency of the final implementation. This article examines the trade-off between the power consumption and flexibility of FPGA clock networks. Specifically, this article makes three contributions. First, it presents a new parameterized clock-network framework for describing and comparing FPGA clock networks. Second, it describes new clock-aware placement techniques that are needed to find a legal placement satisfying the constraints imposed by the clock network. Finally, it performs an empirical study to examine the trade-off between the power consumption of the clock network and the impact of the CAD constraints for a number of different clock networks with varying amounts of flexibility. The results show that the techniques used to produce a legal placement can have a significant influence on power and the ability of the placer to find a legal solution. On average, circuits placed using the most effective techniques dissipate 5% less overall energy and are significantly more likely to be legal than circuits placed using other techniques. Moreover, the results show that the architecture of the clock network is also important. On average, FPGAs with an efficient clock network are up to 14.6% more energy efficient compared to other FPGAs.

This paper describes GlitchLess, a circuit-level technique for reducing power in field-programmable gate arrays (FPGAs) by eliminating unnecessary logic transitions called glitches. This is done by adding programmable delay elements to the logic blocks of the FPGA. After routing a circuit and performing static timing analysis, these delay elements are programmed to align the arrival times of the inputs of each lookup table (LUT), thereby preventing new glitches from being generated. Moreover, the delay elements also behave as filters that eliminate other glitches generated by upstream logic or off-chip circuitry. On average, the proposed implementation eliminates 87% of the glitching, which reduces overall FPGA power by 17%. The added circuitry increases the overall FPGA area by 6% and critical-path delay by less than 1%. Furthermore, since it is applied after routing, the proposed technique requires little or no modifications to the routing architecture or computer-aided design (CAD) flow.

This paper describes a technique that reduces dynamic power in FPGAs by reducing the number of glitches in the global routing resources. The technique involves adding programmable delay elements within the logic blocks of an FPGA to programmably align the arrival times of early-arriving signals to the inputs of the lookup tables and to filter out glitches generated by earlier circuitry. On average, the proposed technique eliminates 91% of the glitching, which reduces overall FPGA power by 18%. The added circuitry increases overall area by 5% and critical-path delay by less than 1%. Furthermore, since it is applied after routing, the proposed technique requires no modifications to the existing FPGA routing architecture or CAD flow.

The programmable clock networks in FPGAs have a significant impact on overall power, area, and delay. Not only does the clock network itself dissipate a significant amount of power, since it connects to every latch on the FPGA and toggles every cycle, but the design of the clock network also affects how efficiently the rest of the application can be implemented since it imposes constraints on the CAD tools which map the application onto the FPGA. To examine this tradeoff, this paper describes and compares new clock-aware placement techniques and then examines how the clock network architecture affects overall power, area, and delay. Our results show that the placement techniques used to make placement clock-aware have a significant influence on power and delay. On average, circuits placed using the most effective techniques dissipate 9.9% less energy and were 2.4% faster than circuits placed using the least effective techniques. Moreover, the results show that the clock network architecture is also important. On average, FPGAs with an efficient clock network were up to 12.5% more energy efficient and 7.2% faster than other FPGAs.

This paper examines the tradeoffs between flexibility, area, and power dissipation of programmable clock networks for Field-Programmable Gate Arrays (FPGA's). The paper begins by describing a parameterized clock network model that describes a broad range of programmable clock network architectures. Specifically, the model supports architectures with multiple local and global clock domains and varying amounts of flexibility at various levels of the clock network. Using the model, the architectural parameters that control the flexibility of the clock network are varied to determine the cost of this flexibility in terms of area and power dissipation. From these experiments, the study finds that area and power costs are highest for networks with flexibility close to the logic blocks. Furthermore, it found that clock networks with local clock domains have little overhead and are significantly more efficient than clock networks without local clock domains for applications with multiple clocks.

This paper examines various activity estimation techniques in order to determine which are most appropriate for use in the context of field-programmable gate arrays (FPGAs). Specifically, the paper compares how different activity estimation techniques affect the accuracy of FPGA power models and the ability of power-aware FPGA CAD tools to minimize power. After comparing various existing techniques, the most suitable existing techniques are combined with two novel enhancements to create a new activity estimation tool called ACE-2.0. Finally, the new publicly available tool is compared to existing tools to validate the improvements. Using activities estimated by ACE-2.0, the power estimates and power savings were both within 1% of the results obtained using simulated activities

Scaling of process technologies and innovations in FPGA architecture and CAD are allowing increasingly more sophisticated applications to be implemented on FPGAs. These applications include system-level designs consisting of many subcomponents that use separate clocks. To support a wide range of applications with different clocking schemes, commercial devices have incorporated high-speed, low-skew clock networks that supply multiple clock signals to logic, memory, and arithmetic elements in the FPGA. The design of these programmable clock networks and of the CAD tools that support them is of utmost importance. Not only does the clock network itself dissipate a significant amount of power, since it connects to every latch on the FPGA and toggles every cycle. But, the design of clock network also affects how efficiently the rest of the circuit can be implemented, since it imposed constraints on the CAD tools that map applications onto the FPGA.