An FPGA Architecture and CAD Flow Supporting Dynamically Controlled Power Gating

© 2015 IEEE.Leakage power is an important component of the total power consumption in field-programmable gate arrays (FPGAs) built using 90-nm and smaller technology nodes. Power gating was shown to be effective at reducing the leakage power. Previous techniques focus on turning OFF unused FPGA resources at configuration time; the benefit of this approach depends on resource utilization. In this paper, we present an FPGA architecture that enables dynamically controlled power gating, in which FPGA resources can be selectively powered down at run-time. This could lead to significant overall energy savings for applications having modules with long idle times. We also present a CAD flow that can be used to map applications to the proposed architecture. We study the area and power tradeoffs by varying the different FPGA architecture parameters and power gating granularity. The proposed CAD flow is used to map a set of benchmark circuits that have multiple power-gated modules to the proposed architecture. Power savings of up to 83% are achievable for these circuits. Finally, we study a control system of a robot that is used in endoscopy. Using the proposed architecture combined with clock gating results in up to 19% energy savings in this application

FPGA implementation of a frame delay

The objective of this thesis is to investigate the applicability of Field Programmable Gate Arrays (FPGAs) for frame delay implementation. FPGAs are programmable devices that can be directly configured by the end user without the use of an integrated circuit fabrication facility. They offer the designer the benefits of custom hardware, eliminating high development costs and manufacturing time. Frame delays are easier to realize using R/W memory where data is written into the memory and read out for each frame. FPGAs are used in a Quartus II environment as it is easy to perform frame delay implementation using schematic entry procedure. Since FPGAs use look-up tables as configurable logic blocks, they are considered as an appropriate choice for frame delay based designs

Analysis of logic block architectures and functional improvement of fine grained cells

The first objective of this research project was to evaluate the performance of various logic block architectures in FPGAs. Since logic blocks widely vary in size, functionality and complexity, we were motivated to explore them in detail. For our study, logic blocks from Actel, Altera, Quicklogic and Xilinx were chosen along with some designs discussed in the academia. These cells were either multiplexer based or look-up-table (LUT) based. Structural VHDL models of all these blocks were constructed and benchmarks circuits were mapped. Results at this stage suggested that, although the coarse grained cells occupied more area and showed poor utilization, they were considerably faster than the fine grained cells; The second objective was to improve the performance of the Actel Proasicplus (fine grained) logic block by enhancing its functional capabilities. During this process we came up with three modified architectures. These new cells were laid out in MAGIC using a TSMC 0.18mum technology file with lambda = 0.09 mum and the extracted files were simulated in PSpice. This transistor level data helped us to estimate the area and propagation delay of the new architectures. The modified architectures were also tested for performance by implementing the previous benchmarks and a significant improvement in speed, occupied area and utilization was observed

A polymorphic hardware platform

In the domain of spatial computing, it appears that platforms based on either reconfigurable datapath units or on hybrid microprocessor/logic cell organizations are in the ascendancy as they appear to offer the most efficient means of providing resources across the greatest range of hardware designs. This paper encompasses an initial exploration of an alternative organization. It looks at the effect of using a very fine-grained approach based on a largely undifferentiated logic cell that can be configured to operate as a state element, logic or interconnect - or combinations of all three. A vertical layout style hides the overheads imposed by reconfigurability to an extent where very fine-grained organizations become a viable option. It is demonstrated that the technique can be used to develop building blocks for both synchronous and asynchronous circuits, supporting the development of hybrid architectures such as globally asynchronous, locally synchronous

Template-based embedded reconfigurable computing

XIV+212hlm.;24c

Hybrid FPGA: Architecture and Interface

Hybrid FPGAs (Field Programmable Gate Arrays) are composed of general-purpose logic resources with different granularities, together with domain-specific coarse-grained units. This thesis proposes a novel hybrid FPGA architecture with embedded coarse-grained Floating Point Units (FPUs) to improve the floating point capability of FPGAs. Based on the proposed hybrid FPGA architecture, we examine three aspects to optimise the speed and area for domain-specific applications. First, we examine the interface between large coarse-grained embedded blocks (EBs) and fine-grained elements in hybrid FPGAs. The interface includes parameters for varying: (1) aspect ratio of EBs, (2) position of the EBs in the FPGA, (3) I/O pins arrangement of EBs, (4) interconnect flexibility of EBs, and (5) location of additional embedded elements such as memory. Second, we examine the interconnect structure for hybrid FPGAs. We investigate how large and highdensity EBs affect the routing demand for hybrid FPGAs over a set of domain-specific applications. We then propose three routing optimisation methods to meet the additional routing demand introduced by large EBs: (1) identifying the best separation distance between EBs, (2) adding routing switches on EBs to increase routing flexibility, and (3) introducing wider channel width near the edge of EBs. We study and compare the trade-offs in delay, area and routability of these three optimisation methods. Finally, we employ common subgraph extraction to determine the number of floating point adders/subtractors, multipliers and wordblocks in the FPUs. The wordblocks include registers and can implement fixed point operations. We study the area, speed and utilisation trade-offs of the selected FPU subgraphs in a set of floating point benchmark circuits. We develop an optimised coarse-grained FPU, taking into account both architectural and system-level issues. Furthermore, we investigate the trade-offs between granularities and performance by composing small FPUs into a large FPU. The results of this thesis would help design a domain-specific hybrid FPGA to meet user requirements, by optimising for speed, area or a combination of speed and area

Programmable flexible cores for SoC applications

Tese de mestrado. Engenharia Electrotécnica e de Computadores. Faculdade de Engenharia. Universidade do Porto. 200

Circuit Design of Programmable Logic and Interconnect Blocks using Spin Transfer Torque RAM for Non-Volatile FPGAs

Most of the Field-Programmable Gate Arrays (FPGAs) are currently SRAM based. The conventional SRAM has been the primary choice for memory storage in the Configurable Logic Blocks (CLBs) as well as for the configuration bits of the reconfigurable interconnects. However SRAM based FPGAs are volatile and needs an external non-volatile memory to store the configuration data. Also SRAM leakage currents increases as technology scales towards lower nodes. The use of non-volatile memories such as Spin-Transfer Torque (STT)-RAM helps to overcome the drawbacks of SRAM-based FPGAs without significant speed penalty. In this paper we present the design of simple non-volatile CLBs using STT-RAM technology. For verifying the design these CLBs have been programmed to implement various functions. The design has been simulated and verified using cadence tools in CMOS 40nm technology